Vitreous solid electrolyte sheets of Li ion conducting sulfur-based glass and associated structures, cells and methods

ABSTRACT

A lithium ion-conductive solid electrolyte including a freestanding inorganic vitreous sheet of sulfide-based lithium ion conducting glass is capable of high performance in a lithium metal battery by providing a high degree of lithium ion conductivity while being highly resistant to the initiation and/or propagation of lithium dendrites. Such an electrolyte is also itself manufacturable, and readily adaptable for battery cell and cell component manufacture, in a cost-effective, scalable manner.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of Ser. No. 16/179,803, filed Nov. 2,2018, titled “VITREOUS SOLID ELECTROLYTE SHEETS OF Li ION CONDUCTINGSULFUR-BASED GLASS AND ASSOCIATED STRUCTURES, CELLS AND METHODS”, whichis a continuation of Ser. No. 14/954,812, filed Nov. 30, 2015, titled“VITREOUS SOLID ELECTROLYTE SHEETS OF Li ION CONDUCTING SULFUR-BASEDGLASS AND ASSOCIATED STRUCTURES, CELLS AND METHODS”, which claimspriority from U.S. Provisional Patent Application 62/086,641, filed Dec.2, 2014, titled LITHIUM ION CONDUCTING GLASS LAYERS AND ASSOCIATEDPROTECTED LITHIUM METAL ELECTRODES AND BATTERY CELLS; and from U.S.Provisional Patent Application 62/111,048, filed Feb. 2, 2015, titledLITHIUM ION CONDUCTING GLASS LAYERS AND ASSOCIATED PROTECTED LITHIUMMETAL ELECTRODES AND BATTERY CELLS; and from U.S. Provisional PatentApplication 62/146,809, filed Apr. 13, 2015, titled FREESTANDING LITHIUMION CONDUCTING ARTICLES AND ASSOCIATED ELECTRODE ASSEMBLIES AND BATTERYCELLS, and from U.S. Provisional Patent Application 62/149,250, filedApr. 17, 2015, titled FREESTANDING LITHIUM ION CONDUCTING ARTICLES ANDASSOCIATED ELECTRODE ASSEMBLIES AND BATTERY CELLS; and from U.S.Provisional Patent Application 62/165,791, filed May 22, 2015, titledLITHIUM ION CONDUCTING WALL STRUCTURES AND LITHIUM ELECTRODE ASSEMBLIESAND ASSOCIATED CONTINUOUS ROLLS AND LITHIUM BATTERY CELLS AND METHODS OFMAKING THEREOF; and from U.S. Provisional Patent Application 62/171,561,filed Jun. 5, 2015, titled STANDALONE INORGANIC SOLID ELECTROLYTESHEETS, AND STANDALONE LITHIUM ION CONDUCTIVE SOLID ELECTROLYTESEPARATORS, CONTINUOUS INORGANIC SEPARATOR ROLLS, LITHIUM ELECTRODEASSEMBLIES, AND BATTERY CELLS THEREOF, AS WELL AS METHODS OF MAKINGTHEREOF; and from U.S. Provisional Patent Application 62/196,247, filedJul. 23, 2015, titled STANDALONE INORGANIC SOLID ELECTROLYTE SHEETS, ANDSTANDALONE LITHIUM ION CONDUCTIVE SOLID ELECTROLYTE SEPARATORS,CONTINUOUS INORGANIC SEPARATOR ROLLS, LITHIUM ELECTRODE ASSEMBLIES,BATTERY CELLS THEREOF, AND METHODS OF MAKING; and from U.S. ProvisionalPatent Application 62/222,408, filed Sep. 23, 2015, titled VITREOUSSOLID ELECTROLYTE SHEETS OF Li ION CONDUCTING SULFUR BASED GLASS ANDASSOCIATED STRUCTURES, CELLS AND METHODS. This application furtherclaims priority from U.S. Provisional Patent Application U.S.Provisional Application 62/126,319, filed Feb. 27, 2015, titledCHARACTERIZATION AND QUALITY CONTROL OF GLASS ELECTROLYTE LAYERS. Eachof these applications is incorporated herein by reference in itsentirety and for all purposes.

STATEMENT OF GOVERNMENT SUPPORT

This invention was made with Government support under Award No.:DE-AR0000349 and/or DE-AR0000772 awarded by the Advanced ResearchProjects Agency-Energy (ARPA-E), U.S. Department of Energy. TheGovernment has certain rights in this invention.

FIELD OF THIS DISCLOSURE

This disclosure relates generally to the field of lithiumelectrochemical devices and lithium components thereof, and inparticular to lithium battery cells, lithium electrode assemblies, andLi ion conducting solid electrolyte components (e.g., separators andsolid electrolyte sheets) for use in lithium battery cells, as well asmethods for making said components, electrode assemblies and batterycells.

BACKGROUND OF THIS DISCLOSURE

There is a continuing need for high performance battery cells and theirassociated cell components, and particularly for high energy densitysecondary batteries.

SUMMARY

Provided herein is a standalone lithium ion-conductive solidelectrolyte, methods of making and using the electrolyte, and batterycells and cell components incorporating the electrolyte. A standalonelithium ion-conductive solid electrolyte in accordance with thisdisclosure can include a freestanding inorganic vitreous sheet ofsulfide-based lithium ion conducting glass capable of high performancein a lithium metal battery by providing a high degree of lithium ionconductivity while being highly resistant to the initiation and/orpropagation of lithium dendrites. Such an electrolyte is also itselfmanufacturable, and readily adaptable for battery cell and cellcomponent manufacture, in a cost-effective, scalable manner.

In one aspect, provided is a standalone Li ion conductive solidelectrolyte separator for use in an electrode assembly or lithiumbattery cell, the separator comprising a freestanding substantiallyamorphous Li ion conductive thin walled solid electrolyte structure(i.e., a wall structure), typically in the form of a dense inorganicsheet, such as a ribbon (i.e., a relatively long narrow sheet), havingsubstantially parallel lengthwise edges, battery serviceable size, andLi ion conductivity ≥10⁻⁵ S/cm, preferably ≥10⁻⁴ S/cm, and morepreferably ≥10⁻³ S/cm.

In various embodiments the freestanding solid electrolyte wall structureis a vitreous solid electrolyte sheet of Li ion conducting sulfur-basedglass that is readily scalable to long continuous lengths (e.g., >25 cm,≥50 cm or ≥100 cm), large areas (e.g., ≥100 cm²), and manufacturablyalterable length (l) to width (w) area aspect ratios (l/w).

For example, in various embodiments the vitreous solid electrolyte sheetof sulfur-based glass is a self-supporting and substrate-less materiallayer having a uniform thickness ≤100 μm, an area aspect ratio no lessthan 10 (e.g., (l/w)≥20), and a width no less than 1 cm (e.g., about2-10 cm wide). In various embodiments the substantially amorphousvitreous sheet is preferably essentially free of crystalline phases, andeven more preferably the vitreous sheet is a homogeneous glass.

In various embodiments the vitreous solid electrolyte sheet is formed asa continuous web from which cut-to-size sheets are excised forincorporation into one or more battery cells and/or electrode assembliesas a solid electrolyte separator or component thereof. In particularembodiments the manufacturing process for making the vitreous web isintegrated into a production process for fabricating lithium electrodeassemblies of the present disclosure and battery cells.

The freestanding substantially amorphous inorganic solid electrolytesheet provided herein is highly conductive of Li ions, and, in variousembodiments, the solid electrolyte sheet is devoid of continuousinterconnected microscopic pathways, which, if otherwise present, couldallow for through penetration of lithium metal dendrites. As used hereinand in the claims, by highly conductive it is meant that the inorganicsolid electrolyte sheet has a room temperature Li ion conductivity of atleast 10⁻⁵ S/cm, preferably at least 10⁻⁴ S/cm, and more preferably atleast 10⁻³ S/cm. Preferably, the inorganic Li ion-conductive sheet issubstantially impenetrable to lithium metal dendrites, and thus, whenemployed as a solid electrolyte separator, the instant sheet, entirelyinorganic, enables the realization of a safe lithium metal secondarybattery cell.

In accordance with the disclosure, the freestanding inorganic solidelectrolyte sheet comprises a continuous inorganic Li ion conductingamorphous solid material phase having an intrinsic room temperature Liion conductivity ≥10⁻⁵ S/cm, preferably ≥10⁻⁴ S/cm, and more preferably≥10⁻³ S/cm. In various embodiments, the continuous inorganic Li ionconducting amorphous material phase is an inorganic glass, and inembodiments the inorganic glass may be characterized as having at leastone glass network former and glass network modifier. In exemplaryembodiments the inorganic glass is a Li ion conducting sulfur-basedglass. In various embodiments the elemental constituents of thesulfur-based glass includes sulfur, lithium and one or more elementalconstituents selected from the group consisting of boron, phosphorous,silicon, germanium, arsenic and oxygen.

In various embodiments, to create a dendrite resistant microstructure,the continuous Li ion conducting glass phase is not only amorphous, andthereby devoid of crystal grains and associated crystalline grainboundaries, it is also characterized as “vitreous” (i.e., a vitreousglass), which is a term used herein to describe a continuous glassphase, glass layer (e.g., a vitreous glass stratum) or glass article(e.g., a vitreous glass sheet) that is formed directly from the melt orderived from a continuous solidified melt, and thus, is not, and doesnot contain, an agglomeration of pressed or discrete glass-powderparticles (e.g., sulfide glass-powder/amorphous-powder particles); andtherefore, the vitreous glass phase (or more simply vitreous phase) orvitreous glass sheet (or more simply vitreous sheet) is also entirelydevoid of glass-powder/amorphous powder inter-particle boundaries, andpreferably absent of microstructural features similar to those thatresult from compacting glass particles, such as an undue density ofinternal pores and surface voids.

In various embodiments the solid electrolyte sheet is a vitreousmonolith wherein the continuous Li ion conducting vitreous glass phase(e.g., sulfur-based glass) is present in an uninterrupted fashionthroughout the entirety of the solid electrolyte sheet, and therewithprovides a continuous vitreous matrix devoid of crystalline grainboundaries and glass-powder inter-particle boundaries. In variousembodiments, the solid electrolyte sheet is a vitreous monolith of a Liion conducting sulfur-containing glass essentially free of crystallineregions. Preferably the vitreous glass sheet is homogeneous, and by thisit is meant that the sheet is essentially free of secondary phases,including crystalline phases and secondary amorphous phases.

The vitreous solid electrolyte sheet of this disclosure is furtheradvantaged by the quality of its bulk and surface, and, in particular,its lack of features. In various embodiments the vitreous sheet hasliquid-like surfaces commensurate with preventing dendrite initiation.The vitreous glass sheet, is not plagued by flaws normally associatedwith powder particle consolidation, such as an undue amount of void-likedefects, including internal micropores and irregularly shaped surfacemicrovoids, both of which are commonplace for die pressed andhot-pressed sulfide glass powder compacts.

In some embodiments, the sulfur-based glass is of a type Li₂S—YS_(n),Li₂S—YS_(n)—YO_(n) and combinations thereof, wherein Y is selected fromthe group consisting of Ge, Si, As, B, or P, and n=2, 3/2 or 5/2, andthe glass is chemically and electrochemically compatible in contact withlithium metal. Suitable glass may comprise Li₂S and/or Li₂O as a glassmodifier and one or more of a glass former selected from the groupconsisting of P₂S₅, P₂O₅, SiS₂, SiO₂, B₂S₃ and B₂O₃. In someembodiments, the glass may be devoid of phosphorous.

In another aspect this disclosure is directed to methods of makinghighly conductive and freestanding vitreous solid electrolytes, (e.g.,discrete Li ion conducting solid electrolyte glass sheets). In variousembodiments the vitreous sheet is formed by continuous manufacturingprocesses, which are readily scalable to long continuous lengths, largeareas and alterable length to width aspect ratios, including making astandalone continuous web of vitreous Li ion conducting sulfur-basedglass.

In various embodiments the method of making the vitreous solidelectrolyte glass sheet involves forming a vitreous Li ion conductivesulfur-based glass into a thin inorganic fluid sheet of unbrokencontinuity (e.g., a liquid glass stream), and, while ensuring that thelengthwise edges are unconstrained, causing or allowing the fluid sheetto flow, as a fluid stream, along its lengthwise dimension withsubstantially parallel lengthwise edges.

In various embodiments significant advantage is realized by solidifyingthe fluid glass stream in the absence of foreign solid contact. Forinstance, the vitreous sheet solidified such that its first and secondprincipal side surfaces are untouched by a foreign solid surface, andthus are chemically and physically pristine in their virgin state as asolid—yielding benefit as it pertains to surface smoothness, flaws, andpurity, and, in particular, minimizing surface contaminants as well asfacilitating a high quality liquid-like surface in the absence ofpolishing.

In various embodiments the thickness of the solid electrolyte sheet inits virgin state as a solid is of a pre-determined and uniform value,and by this expedient circumvents the need to cut or grind down thesurfaces in order to achieve a desired thickness, and therefore theprincipal side surfaces may be kept untouched by an abrasive foreignsolid surface during sheet manufacture and storage.

Accordingly, in various embodiments, the first and second principal sidesurfaces of the solid electrolyte sheet are not subjected to one or moreof the following post-solidification processes: mechanical grinding,in-plane slicing (i.e., cutting parallel to the principal opposingsurfaces), or polishing. The ability to achieve a thin and uniformthickness in the virgin state is highly beneficial as it eliminatescostly processing steps and circumvents damage (e.g., surface flaws)that might otherwise arise by thinning (e.g., grinding).

In various embodiments the method of making the freestanding vitreoussheet or web of Li ion conducting glass is by drawing. In variousembodiments the drawing process is continuous. In various embodimentsthe drawing method is a melt draw, preform draw or a capillary draw.

In various embodiments the method of making the vitreous solidelectrolyte sheet of Li ion conducting sulfur-based glass involvesselecting and adjusting the constituent elements of the glass to effectparticular properties desirable for processing and/or performance in abattery cell. These properties include one or more of the glassstability factor, liquidus viscosity, Li ion conductivity and chemicalas well as electrochemical compatible with lithium metal.

In another aspect provided is a long continuous vitreous sheet of Li ionconducting glass in the form of a vitreous web. Discrete freestandingsolid electrolyte sheets may be cut-to-size from the web by lasercutting along its widthwise and/or lengthwise dimension. In variousembodiments the continuous web of vitreous Li ion conducting glass issufficiently large in area (or length) to yield a plurality ofcut-to-size solid electrolyte sheets, or the web may serve as asubstrate for downstream processing of battery cell components,including electrode subassemblies and electrode assemblies of thepresent disclosure.

In various embodiments the vitreous Li ion conducting glass web haslength greater than 50 cm and width between 1 cm to 10 cm, and typicallygreater than 100 cm long, such as hundreds of centimeters long (e.g., atleast 100 cm, 200 cm, 300 cm, 400 cm, 500 cm, 600 cm, 700 cm, 800 cm,900 cm, or at least 1 meter in length). Typically the web has uniformthickness less 500 μm.

Preferably, the vitreous web of solid electrolyte glass is flexible, andsufficiently robust when flexed to be configurable (without fracture) asa continuous coil of glass, typically wound about a spool, for storage,transportation and component manufacture. For instance, the continuouscoil serving as a source/supply roll of vitreous sheet for roll-to-roll(R₂R) manufacturing of downstream battery cell components, includingelectrode subassemblies, electrode assemblies, and battery cells of thepresent disclosure. Preferably, the solid electrolyte web, as formed,has sufficient surface quality and thickness uniformity that it requiresno post solidification grinding and/or polishing.

Various processing steps are contemplated herein for improving thequality and performance of the vitreous solid electrolyte web/sheet aswell as for making downstream battery cell components, including: i)removing, by laser cutting, low quality peripheral edge portions; ii)fire polishing the surfaces/edges; iii) incorporating edge-protectorelements that interface with the sheet along its lengthwise edges; iv)and coating the first and/or second principal side surfaces of the sheetwith a thin material layer, typically <1 μm thick (e.g., a tie-layer onthe first principal side surface for enhancing the interface between thesolid electrolyte sheet in direct contact with a lithium metal layer, ora physical vapor deposited dense Li ion conducting inorganic materiallayer on the first/second principal side surface for improving chemicalcompatibility with battery cell components).

In another aspect the disclosure provides an electrode subassembly,which is a substrate laminate composed of the vitreous solid electrolytesheet coated on its first principal side with a material tie-layerand/or current collector layer that functions to facilitate anelectrochemically effective solid-state interface with a lithium metallayer subsequently deposited on its surface during the formation of astandalone lithium metal electrode assembly of the present disclosure,or the formation of the lithium metal layer may be realized within theconfines of a battery cell during initial charge. In various embodimentsdepositing the tie-layer layer and/or current collector layer directlyonto a vitreous solid electrolyte web, including making use of sheet toroll and R₂R manufacturing, forms a continuous web of electrodesubassemblies.

In another aspect the disclosure provides a standalone electrodeassembly comprising the instant solid electrolyte wall structure (e.g.,a substantially impervious vitreous solid electrolyte sheet) and anelectroactive material, typically as part of an electroactive componentlayer (e.g., a multi-layer) having first and second major opposingsurfaces. For example, the electroactive component layer may be abi-layer of an electroactive material layer (e.g., lithium metal) on acurrent collecting layer, or a tri-layer of a current collector layersandwiched between a pair of lithium metal layers, or more generallyelectroactive material layers.

The standalone electrode assembly may be a negative or positiveelectrode assembly, depending on the nature of the electroactivematerial, and its intended use in a battery cell.

In various embodiments the standalone electrode assembly is termed“solid-state” in that it contains a solid-state laminate composed of theelectroactive component layer encapsulated in direct contact on at leastone major surface by the first principal side surface of the vitreoussolid electrolyte sheet. The direct contact between the electroactivecomponent layer and the vitreous solid electrolyte sheet forms asolid-state interface that is, and remains, devoid of liquid (includingliquid electrolytes). In various embodiments the electroactive materialis lithium metal, and the solid-state interface is made from a denselithium metal layer in direct contact with the vitreous solidelectrolyte sheet. In alternative embodiments, the solid-state electrodeassembly has an electroactive component layer comprising a powderparticle composite of electroactive particles (e.g., having a potentialwithin about 1V of lithium metal, such as intercalatable carbons), andglass or glass-ceramic particles highly conductive of Li ions (e.g.,sulfur-based glasses/glass ceramics).

In various embodiments the standalone electrode assembly may be termed“single-sided” or “double-sided” depending on whether one or both of themajor opposing sides of the electrode assembly is electrochemicallyfunctional in that it allows electrical through migration of Li ions. Adouble-sided assembly is electrochemically operable on both of itssides, whereas a single-sided assembly is operable on just one side.When double sided, the electrode assembly includes a second solidelectrolyte sheet of the present disclosure. For example, indouble-sided solid-state lithium metal electrode assembly, the firstprincipal side surfaces of the first and second solid electrolyte sheetsform a solid-state interface with lithium metal of the electroactivecomponent layer.

In various embodiments the standalone electrode assembly is sealed toprevent external constituents from contacting the electroactive materialinside the assembly, and to prevent internal constituents (e.g., liquidelectrolytes, when present) from seeping out.

In various embodiments the negative electrode assembly is a sealedsolid-state lithium metal negative electrode assembly, typicallydouble-sided.

In other embodiments, the sealed electrode assembly is not solid-state,and includes a liquid phase electrolyte at the interface between thesolid electrolyte sheet and the electoactive material, to enhanceelectrochemical performance. For example, a double-sided positiveelectrode assembly comprising a liquid electrolyte that is sealed insidethe assembly in direct contact with a Li ion intercalation compound asthe electroactive material of the assembly (e.g., having a potential vs.lithium metal greater than 3V, and preferably greater than 4V).

In another aspect provided herein are lithium battery cells comprisingthe solid electrolyte separator of the present disclosure. In variousembodiments the cells are of a wound or folded construction, and thesolid electrolyte separator is sufficiently flexible to be wound as suchwithout fracture.

In various embodiments, the battery cell has a hybrid cell constructioncomprising a sealed electrode assembly (e.g., a sealed solid-statelithium metal negative electrode assembly); an opposing electrode (e.g.,a positive electrode), and a liquid electrolyte in direct touchingcontact with the positive electrode but unable to contact the lithiummetal inside the sealed assembly.

In some embodiments, the battery cell is fully solid state, and thusdevoid of a liquid phase electrolyte.

In other embodiments, the battery cell includes a common liquidelectrolyte in direct contact with the positive and negative electrodeof the cell, with the solid electrolyte separator of the presentdisclosure providing a wall structure disposed between the electrodes toimprove battery cell safety, especially as it pertains tomitigating/preventing thermal runaway. For example, the solidelectrolyte separator disposed between intercalation electrodes in anotherwise conventional lithium ion battery cell.

In other aspects the disclosure provides methods for making theaforesaid lithium battery cells. In various embodiments, the methodinvolves R₂R manufacturing, or sheet-to-roll, or roll-to-sheetprocessing.

In yet other aspects the disclosure provides methods for assessing andinspecting the quality of the instant vitreous solid electrolyte sheets,electrode sub-assemblies and lithium electrode assemblies. In variousembodiments the inspection is performed inline with fabricating thesheet or web (e.g., inline with drawing of the vitreous Li ionconducting glass).

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-D illustrate a freestanding Li ion conducting solid electrolytesheet of this disclosure.

FIGS. 1E-F illustrate a freestanding Li ion conducting solid electrolytesheet of this disclosure and a mother-sheet from which it is excised.

FIG. 1G illustrates a freestanding Li ion conducting solid electrolytesheet of this disclosure having a discrete edge-protector element.

FIG. 1H illustrates an electrode subassembly of this disclosure.

FIGS. 2A-B illustrate freestanding Li ion conducting solid electrolytewall structures in accordance with various embodiments of the instantdisclosure.

FIG. 3A illustrates a continuous roll of the instant solid electrolytesheet wound on a spool.

FIG. 3B illustrates a continuous roll of the instant Li ion conductingsolid electrolyte sheet in the form of a web from which individualdiscrete solid electrolyte sheets are excised and stacked.

FIGS. 4A-H illustrate cross sectional views of Li ion conductive solidelectrolyte sheets in accordance with various embodiments of thedisclosure.

FIG. 4 I illustrates a cross sectional view of a lithium metal layer andsolid electrolyte sheet having a surface flaw.

FIGS. 5A-C illustrate various electrode and battery assemblies inaccordance with the instant disclosure.

FIGS. 6A-E illustrate apparatus' for making a freestanding Li ionconducting solid electrolyte sheet in accordance with variousembodiments of the disclosure: FIGS. 6A-B illustrate a fusion drawapparatus; FIG. 6C illustrate a slot draw apparatus; and FIG. 6Dillustrate a preform draw apparatus; and FIG. 6E illustrate a floatprocess.

FIGS. 7A-C illustrate flowcharts for methods of making a continuoussolid electrolyte sheet of this disclosure.

FIG. 8 illustrates a fabrication system and method for making acontinuous web of the instant freestanding Li ion conducting solidelectrolyte sheet in the form of a continuous roll; the web configuredusing an inline sheet to roll process.

FIG. 9 illustrates a method of making a vitreous solid electrolyte sheetin accordance with an embodiment of the disclosure, the method involvingthe use of capillary force to infiltrate a molten glass of the solidelectrolyte between adjacent smooth plates.

FIG. 10A-C illustrates methods of making a vitreous solid electrolytesheet in accordance with an embodiment of the disclosure.

FIGS. 11A-B illustrate electrode subassemblies in accordance withvarious embodiments of this disclosure.

FIGS. 12A-C illustrates a fabrication system and methods for making anelectrode subassembly and a continuous web of multiple electrodesubassemblies in accordance with an embodiment of the disclosure.

FIG. 13A illustrates a cross sectional depiction of a lithium metalelectrode assembly in accordance with this disclosure.

FIGS. 13B-D illustrate methods of making a lithium electrode assembly inaccordance with various embodiments of this disclosure.

FIGS. 13E-G illustrate cross sectional depictions of backplaneencapsulated lithium metal electrode assemblies, in accordance withvarious embodiments of this disclosure.

FIGS. 13H-J illustrate cross sectional depictions of edge sealed lithiummetal electrode assemblies, in accordance with various embodiments ofthis disclosure.

FIGS. 13K-L illustrate cross sectional depictions of lithium metalelectrode assemblies having an unconstrained backplane architecture, inaccordance with various embodiments of this disclosure.

FIG. 14A-C illustrate fabrication systems and methods for making alithium metal electrode assembly and a continuous web and source rollthereof, the web configured using inline sheet to roll or R₂R processingmethods in accordance with embodiments of this disclosure.

FIG. 15 illustrates a positive lithium electrode assembly in accordancewith this disclosure.

FIGS. 16A-E illustrate battery cells in accordance with variousembodiments of this disclosure. In various embodiments the battery cellis a solid-state cell; a cell having a common liquid electrolyte; ahybrid cell having a sealed electrode assembly of this disclosure; acell constructed with a lithium metal free laminate; and a hybrid cellhaving a positive electrode assembly of this disclosure.

FIG. 17 illustrates the use of light attenuation for inspecting astandalone Li⁺ ion conducting vitreous sheet disclosure, in accordancewith a method disclosure.

FIG. 18 illustrates the use of light reflection for inspecting anelectrode subassembly disclosure, in accordance with a methoddisclosure.

FIGS. 19A-B illustrate the use of light reflection for inspecting alithium electrode assembly disclosure, in accordance with a methoddisclosure.

FIG. 20 illustrates a schematic plot illustrating changes in reflectionfrom an inner metal surface in contact with an instant vitreous sheetafter bringing lithium metal into contact with an outer metal surface.

FIGS. 21A-B illustrate apparatus' for measuring positional resistance ofa vitreous solid electrolyte sheet in a solid-state battery celldisclosure, in accordance with a method disclosure.

FIGS. 22A-B illustrate apparatus' for measuring positional resistance ofa vitreous solid electrolyte in a battery cell disclosure having aliquid phase electrolyte, in accordance with a method disclosure.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Reference will now be made in detail to specific embodiments of thisdisclosure. Examples of the specific embodiments are illustrated in theaccompanying drawings. While this disclosure will be described inconjunction with these specific embodiments, it will be understood thatit is not intended to limit this disclosure to such specificembodiments. On the contrary, it is intended to cover alternatives,modifications, and equivalents as may be included within the spirit andscope of this disclosure. In the following description, numerousspecific details are set forth in order to provide a thoroughunderstanding of this disclosure. This disclosure may be practicedwithout some or all of these specific details. In other instances, wellknown process operations have not been described in detail in order notto unnecessarily obscure this disclosure.

In one aspect, this disclosure is directed to a standalone Li ionconductive solid electrolyte for use in a lithium battery cell, theelectrolyte comprising a dense freestanding inorganic and substantiallyamorphous Li ion conductive solid electrolyte wall structure typicallyin the form of a glass sheet, such as a ribbon (i.e., a relatively longnarrow sheet), having substantially parallel lengthwise edges, batteryserviceable size, and Li ion conductivity ≥10⁻⁵ S/cm, preferably ≥10⁻⁴S/cm, and more preferably ≥10⁻³ S/cm.

The freestanding substantially amorphous solid electrolyte sheet of thepresent disclosure is highly conductive of Li ions, and, in variousembodiments, the sheet is devoid of microscopic pathways, which, ifotherwise present, would allow for through penetration of lithium metaldendrites. By highly conductive it is meant that the solid electrolytesheet has room temperature (i.e., 25° C.) Li ion conductivity of atleast 10⁻⁵ S/cm, preferably at least 10⁻⁴ S/cm, and more preferably atleast 10⁻³ S/cm. In various embodiments, the Li ion conductive sheet issubstantially impenetrable to lithium metal dendrites, and thus, whenemployed as a solid electrolyte separator component, the instant sheet,entirely inorganic, enables the realization of a safe lithium metalsecondary battery cell.

By use of the term “substantially impenetrable,” as it pertains tolithium metal dendrites, it is meant within the context of the instantwall structure (e.g., solid electrolyte sheet) configured in a lithiumbattery cell, and it means that over the service life of the batterycell, lithium metal dendrites are unable to penetrate across the sheet,and preferably cannot extend deeply or at all into the bulk of the solidelectrolyte sheet (e.g., beyond 10% of the sheet thickness), and by thisexpedient the referenced battery cell is resistant to electricalshorting and fracture that might otherwise result from dendriticin-growth of lithium metal into pre-existing flaws or microstructuralfeatures on or nearby the sheet surface.

For example, when a substantially lithium dendrite impenetrable solidelectrolyte sheet of the present disclosure is incorporated in a lithiummetal battery cell as a separator layer adjacent to and in directcontact with a lithium metal electroactive layer, lithium metal deposits(e.g., lithium dendrites) are unable to penetrate deeply, if at all,into the bulk of the separator sheet during normal battery cellcharging. Preferably, lithium metal deposits are unable to penetratemore than 10 μm into the bulk of the sheet; and preferably no more than5 μm, more preferably no more than 1 μm, and even more preferablylithium metal deposits are completely unable to penetrate thesurface—the sheet, therefore, dendrite impenetrable.

In accordance with the disclosure, the freestanding solid electrolytesheet comprises a continuous inorganic Li ion conducting amorphousmaterial phase having intrinsic room temperature Li ion conductivity≥10⁻⁵ S/cm, preferably ≥10⁻⁴ S/cm, and more preferably ≥10⁻³ S/cm. Invarious embodiments, the continuous inorganic Li ion conductingamorphous material phase is an inorganic glass, and in embodiments theinorganic glass may be characterized as having at least one glassnetwork former and at least one glass network modifier. To realize therequisite ionic conductivity in an inorganic amorphous phase, in variousembodiments it is a Li ion conducting sulfur-based glass. In variousembodiments the elemental constituents of the sulfur-based glass includesulfur, lithium and one or more elemental constituents selected from thegroup consisting of silicon, germanium, boron, phosphorous, arsenic andoxygen.

In various embodiments the freestanding solid electrolyte wall structureis a discrete substrate-less material layer in the form of a thin, longand relatively narrow sheet of sulfur-containing glass havingsubstantially parallel lengthwise edges. For instance, in variousembodiments the solid electrolyte sheet is a glass strip or ribbon ofsubstantially uniform thickness ≤500 μm; length dimension (l)≥10 cm;width dimension (w)≥1 cm; and area aspect ratio (l/w)≥10, and moretypically ≥20. Preferably the freestanding solid electrolyte sheet issufficiently robust when flexed to be woundable for storage or forincorporation into a battery cell of wound or folded construction.

When using the term “substantially uniform thickness” it is meant thatthe thickness of the solid electrolyte sheet is sufficiently uniform forits intended purpose as a solid electrolyte sheet in a battery cell.When using the term “uniform thickness” (e.g., with respect to thethickness of the solid electrolyte sheet or a fluid stream of glass, itis meant that the thickness variation is at most 20% of the averagethickness (t), and more preferably less. In embodiments, wherein theaverage thickness is 250 μm≤t<500 μm, the thickness variation ispreferably ≤2%, and more preferably ≤1%; in embodiments wherein theaverage thickness is 100 μm≤t<250 μm, the thickness variation ispreferably ≤5%, and more preferably ≤2%; in embodiments wherein theaverage thickness is 50 μm≤t<100 μm the thickness variation ispreferably ≤10%, and more preferably ≤5%, and more preferably ≤2%; inembodiments wherein the average thickness is 10 μm≤t<50 μm the thicknessvariation is preferably ≤20%, more preferably ≤10%, even more preferably≤5%; and yet even more preferably ≤2%; and in embodiments wherein theaverage thickness is 5 μm≤t<10 μm the thickness variation is preferably≤20%, more preferably ≤10%, and even more preferably ≤5%.

In various embodiments the freestanding solid electrolyte sheet isformed by a continuous manufacturing process that is readily scalable toachieve long continuous lengths (e.g., ≥50 cm), large areas (e.g., ≥100cm²), manufacturably adjustable area aspect ratios, and flexibilitycommensurate with winding. In various embodiments the sulfide glasssheet is formed as a continuous web, where from discrete sheets may becut-to-size to yield solid electrolyte separators for incorporation intoone or more battery cells and/or electrode assemblies. Preferably, thecontinuous web is sufficiently flexible to be stored as a coil; forexample, wound about a spool to yield a standalone continuous supplyroll of inorganic Li ion conducting sulfide glass ribbon, preferablyessentially free of crystalline phases. In various embodiments themanufacturing process for making the Li ion conducting sulfide glasssheet or web is integrated into a production process for fabricatinglithium electrode assemblies of the present disclosure and battery cellsthereof.

Generally the continuous inorganic Li ion conducting sulfur-based glassphase constitutes a majority volume fraction of the solid electrolytesheet, and thus is considered the primary material phase. In variousembodiments the volume fraction of the continuous primary glass phase isat least 50%, or at least 60%, or at least 70%, or at least 80% of theoverall solid volume of the sheet. In particular embodiments the volumefraction is at least 90% or at least 95% of the overall solid volume,and in preferred embodiments it constitutes about 100%, and thus, insuch embodiments, the solid electrolyte sheet essentially consists ofthe Li ion conducting sulfur-based glass phase. When the volume fractionis less than 100%, the remaining solid volume is generally accounted forby secondary phase(s), which may be crystalline or amorphous. In variousembodiments, the continuous Li ion conducting primary glass phaseeffectively serves as a glass matrix with any secondary phases (ifpresent) typically embedded and isolated therein. In various embodimentsthe continuous Li ion conducting sulfur-based glass phase is the primarymaterial phase of the sheet, as defined above, and it constitutes amajority area fraction of the first and/or second principal sidesurfaces (e.g., at least 50%, at least 60%, at least 70%, at least 80%,at least 90%, or at least 95%, and preferably 100% of the first and/orsecond principal side surface(s) is defined by the continuous Li ionconducting glass phase).

By use of the term “substantially amorphous” when referring to theinstant solid electrolyte sheet or a surface thereof, it is meant toallow for the possibility that the sheet may contain some amount ofcrystalline phases. Typically the crystalline phases are incidental,generally non-conductive (<10⁻⁸ S/cm), and isolated within the amorphousmatrix of the primary Li ion conducting glass phase. However, it iscontemplated that, when present, the crystalline phase may be somewhatconductive of Li ions (≥10⁻⁸ S/cm), and in some instances theconductivity of the crystalline phase may be greater than that of theprimary glass phase. To be considered substantially amorphous, however,the volume fraction of crystalline phases in the solid electrolyte sheetshould be less than 20 vol %, and more typically less than 10 vol %.Preferably the freestanding inorganic solid electrolyte sheet iscompletely amorphous, and as such is entirely devoid of detectablecrystalline phases. In all circumstances, however, the crystallinephases, if present, do not, alone or in combination with each other,create continuous interconnected grain boundaries that extend across thethickness of the sheet, as this would create microscopic pathways forpotential dendrite growth and through penetration. In alternativeembodiments, it is contemplated that the solid electrolyte sheet isprimarily amorphous, with a volume fraction of crystalline phases thatis less than 50% (i.e., between 50 to 20%). In such embodiments, thecrystalline phases are generally conductive of Li ions (>10⁻⁸ S/cm andpreferably >10⁻⁷ S/cm), and more preferably highly conductive (e.g.,>10⁻⁵ S/cm), and in some embodiments it is contemplated that thecrystalline phase is more conductive of Li ions than the continuousamorphous glass matrix in which it is embedded (e.g., >10⁻⁴ S/cm or>10⁻³ S/cm). As described in more detail below, in various embodiments,the substantially amorphous solid electrolyte sheet is essentially freeof crystalline phases, and more preferably no crystalline phases aredetectable.

In various embodiments the freestanding inorganic solid electrolytesheet is amorphous as determined by X-ray diffraction (XRD), and thusdoes not produce a discrete diffraction pattern. In various embodiments,in addition to being amorphous by X-ray diffraction, the solidelectrolyte sheet is preferably essentially free of crystalline phases,and even more preferably contains no detectable crystalline regions asdetermined by XRD, microscopy and/or optical methods. For the avoidanceof doubt, by use of the term amorphous, it is meant that the constituentatoms are arranged in spatial patterns that exhibit no long-range order.

By use of the term “essentially free of crystalline phases,” whenreferring to the solid electrolyte sheet, it is meant to allow for thepossibility that it (the sheet) may contain a very small amount ofcrystalline phases, such as incidental and isolated random nanocrystals,that are undetectable by XRD, but if present, account for no more than5% of the total sheet volume, and preferably no more than 2%, even morepreferably no more than 1%; and yet even more preferably, whenessentially free of crystalline phases, the sheet is completely devoidof crystalline phases (i.e., none are detectable). Likewise, when usingthe term “essentially free of secondary amorphous phases” it is meant toallow for the possibility that the sheet may contain a very small volumefraction of secondary amorphous phases, but no more than 5% of the totalsheet volume, and preferably no more than 2%, and even more preferablyno more than 1%; and yet even more preferably, when essentially free ofsecondary phases, the sheet is preferably devoid of secondary amorphousphases (i.e., none are detectable).

When referring to the instant wall structure (e.g., in the form of asolid electrolyte sheet) as “freestanding” or “freestandable” it ismeant that the sheet is a self-supporting layer that displays amechanical strength (e.g., tensile strength) sufficient to allow it (thesheet) to remain intact in the absence of a substrate (i.e.,self-supporting), and thereby the freestanding solid electrolyte sheetis not dependent upon another self-supporting layer for its continuousintact existence (e.g., a positive or negative electrode layer or aninert carrier film). Accordingly, in various embodiments the instantfreestanding solid electrolyte sheet is “substrate-less.”

By use of the term “standalone solid electrolyte separator” or“standalone solid electrolyte sheet” or “standalone solid electrolyte”it is meant that the separator or sheet or electrolyte is a discretebattery cell component, and thus is not, or has not yet beenincorporated in a battery cell or an electrode assembly. When referringto the sheet or separator as a discrete battery cell component it isunderstood that the sheet or separator is absent of a positive ornegative electrode, and furthermore devoid of electroactive materialthat would otherwise serve to provide ampere-hour capacity to a lithiumbattery cell. In various embodiments, at certain periods of time thestandalone solid electrolyte sheet, freestanding and substrate-less,will have free principal opposing side surfaces that are directlyexposed, or exposable, to the ambient environment in which it (thesheet) is stored or made; accordingly, during those periods, the sheetis not covered by a different material layer onto which the sheet ischemically bonded or physically adhered (permanently or temporarily).The term discrete is also sometimes used herein when referring to acut-to-size solid electrolyte sheet that is excised from a mother-sheetof glass or from a long continuous web of Li ion conducting glass. Byuse of the term standalone when referring to an electrode assembly it ismeant that the electrode assembly has not yet been combined with asecond electrode of opposite polarity, and therefore the standaloneelectrode assembly has not yet been incorporated in a battery cell.

By “electroactive material” it is meant electroactive material thatprovides ampere-hour capacity to a lithium battery cell, and involveslithium in the electrochemical redox reaction (e.g., lithiumintercalation materials and lithium metal).

By use of the term “wall structure” it is typically meant a thinsheet-like solid electrolyte, such as a continuous strip or ribbonhaving substantially parallel lengthwise edges. According to someembodiments, it is contemplated that the wall structure may take theform of a hollow prism-like receptacle, including rectangular andelliptical prisms. In alternative embodiments it is contemplated thatthe solid electrolyte wall structure may be flat with a circular or ovalfootprint.

When referring to a certain property/characteristic of the sheet as“battery serviceable,” it is meant that the referenced characteristic issuitable to support the service of the sheet as a continuous Li ionconducting solid electrolyte separator component in a battery cell ofdefined type (e.g., liquid, gel, polymer or solid-state), form (e.g.,wound, folded or stacked), dimension and/or having one or morepredefined parameters, including, but not limited to, battery cell ratedampere-hour capacity (Ah), area ampere-hour capacity (mAh/cm²),volumetric energy density (Wh/l), and current density (mA/cm²).

By use of the term area specific resistance (ASR) it is meant theresistance of the solid electrolyte sheet as measured between opposingprincipal side surfaces, in contact with either blocking electrodes(e.g., gold coatings or platinum layers) or non-blocking electrodes(typically lithium metal). When measured against blocking electrodes,the ASR is generally at its lowest value because it is simply a measureof the ionic resistance, related to Li ion conductivity and thickness.In contrast, when measured against non-blocking Li metal electrodes, theASR values are indicative of the interfacial resistance against Li metalas well as the ionic resistance of the sheet itself.

By use of the term “intrinsic,” or “intrinsically conductive,” whenreferring to the ionic conductivity of a material, it is meant theinherent conductivity of the material itself, in the absence of anyother additional material agents, such as, for example, liquid solventsor organic molecules or organic material phases.

When referring to the instant solid electrolyte sheet as “inorganic” itis meant that the solid electrolyte sheet is entirely inorganic, andthereby devoid of organic material. The term “organic material” as usedherein, means compounds containing carbon wherein the carbon istypically bonded to itself and to hydrogen, and often to other elementsas well. Thus, the term “inorganic material” means any material that isnot an organic material.

By use of the term “web” or “continuous web” when referring to the solidelectrolyte sheet, it is meant an uninterrupted sheet of such continuouslength that it may serve as a source for multiple discrete/individualsolid electrolyte separator sheets, which are excised from the web(e.g., cut-to-size), for use in one or more battery cells or batterycell components. In various embodiments, the web of solid electrolytesheet is stored, transported or used in downstream manufacture in theform of a roll, such as a supply roll or source roll. However, theinvention is not limited as such and it is contemplated that discretesolid electrolyte sheets may be cut-to-size in-line with webfabrication, and by this expedient, by passing the rolling process. Itis also contemplated that the continuous web may serve as a substratefor downstream cell component manufacture, such as by coating orlaminating material layers to the web; for instance, in the forming ofan electrode-subassembly web from which multiple subassemblies may becut-to-size, or an electrode-assembly web for making cut-to-sizemultiples thereof.

When referring to the instant solid electrolyte sheet as “dense,” it ismeant that the density of the solid electrolyte sheet approaches that ofthe theoretical material from which it is formed, and is typically >90%of theoretical density, and more typically >95%, and preferably >98%(e.g., >99%).

Preferably, the dense solid electrolyte sheet is “substantiallyimpervious” to liquids it comes into contact with during manufacture oroperation of a device in which the sheet is incorporated. Accordingly,the substantially impervious sheet, typically dense, is devoid ofthrough porosity such as pinholes, or, more generally, any pathwaythrough which a liquid might seep across the sheet. Notably, thecriterion of substantial imperviousness to liquids is insufficient toyield a sheet that is substantially impenetrable to lithium metaldendrites. For instance, polycrystalline material layers (e.g.,polycrystalline ceramics) that are substantially impervious to fluids(e.g., gases and/or liquids) are nonetheless highly susceptible tolithium metal dendrite penetration via continuous grain boundarypathways. Accordingly, in various embodiments, the substantiallyamorphous solid electrolyte glass sheets of the present disclosure areboth substantially impervious to liquids they come into direct contactwith and substantially impenetrable to lithium metal dendrites.

In contrast to polycrystalline ceramic layers or powder compacts, thesubstantially amorphous solid electrolyte sheet of the presentdisclosure is devoid of continuous microscopic pathways, such ascontiguous (i.e., interconnected) crystalline grain boundaries orpressed powder inter-particle boundaries, or such boundaries incombination with voids and/or cracks which alone or in combinationcreate a continuous microscopic pathway, extending between the first andsecond principal side surfaces, and, which, if otherwise present, couldprovide a direct path for dendrite through penetration across the sheet.For example, the cavities and voids on the surface of a pressed powdercompact are highly detrimental to dendrite impenetrability as theycreate highly localized hot spots for current focusing, which can leadto very high local current densities, followed by in-growth of Li metaland through penetration; for example, via crack propagation as materialbridges between internal pores inside the powder compact collapse and/orthe local current density at the hot spot reaches such a high value thatsolid Li metal penetrates across.

By “particle-to-particle boundaries” or “inter-particle boundaries” itis meant particle interfaces, including interfaces between regions ofconsolidated polycrystalline powder-particles, glass-ceramicpowder-particles, and amorphous powder-particles (e.g., glassparticles), and mixtures thereof; especially amorphous powder-particleto amorphous powder-particle boundaries and interfaces between compactedregions of pressed powder-particles that generally manifest in a pressedpowder compact as discontinuities in the form of micro-cracks and voids(e.g., chain-like microvoids). By use of the term particle-to-particleboundary, particle boundary or inter-particle boundary it is referringto the boundary between consolidated powder-particles and compactedregions thereof, whereas crystalline grain boundaries are the interfacebetween crystal grains of different crystalline orientation.

Accordingly, the solid electrolyte sheet of this disclosure is not apolycrystalline Li ion conducting ceramic membrane (e.g., a garnet-likeor LTP/LGP membrane or derivatives thereof such as LATP membrane), noris it a simple compact or hot pressed sinter of consolidated Li ionconducting sulfide glass powder-particles, for which obvious or residualinter-particle boundaries, or manifestations thereof, such as surfacevoids and internal pores, are generally unavoidable in manufacture, andthe liquid-like surface lacks flaw manifestations of a pressed powdercompact that are sufficient to initiate Li dendrite penetration. By useof the acronym LTP or LGP membrane it is meant a polycrystallinemembrane based on Lithium Titanium Phosphate or Lithium GermaniumPhosphate, and when a fraction of the titanium is replaced by Aluminum,the acronym LATP is commonly used. LTP or LGP polycrystalline ceramicmembranes, and their compositional derivatives, may be fabricated byconventional solid-state sintering or by using a glass to ceramicapproach. However, regardless of processing, LTP/LGP materials must befully crystallized to be Li ion conductive, and thus only have batteryutility as a polycrystalline membrane.

In a glass powder compact, the presence of microscopic inhomogeneities,such as microvoids and microcracks, are generally unavoidable. And whilecertain processes, such as heated die compaction, if performed over anextended period of time under high uniaxial pressure at or near theglass transition temperature, may provide some relief in theconcentration and/or size of internal voids and cracks in a relativelythick pellet, hot compaction is a costly discontinuous batch processes,that is impractical as well as inadequate for eliminating surface flaws,and especially problematic for making thin pellets. During heated powdercompaction, surface cavities are generated to account for void volumereduction at the particle interfaces, and if gaseous diffusion islimiting, other features including a scattering of internal pores(including micropores and nanopores) can appear distributed throughoutthe interior portion of the compact. For instance, thick hot pressedpowder pellets, even if translucent or seemingly transparent, have ashort finish due to the presence of pitted flaws on their surface, andinternal pores will present as surface voids if the pellet issubsequently ground. Surface imprints and surface contamination willalso diminish the surface quality, especially if pressing is performednear or at about T_(g).

To create a dendrite resistant microstructure, the continuous Li ionconducting glass phase is not only amorphous, and thereby devoid ofcrystalline grains and associated grain boundaries, it is also“vitreous” (i.e., a vitreous glass), which is a term used herein todescribe a glass phase, glass layer (e.g., a vitreous glass stratum), orglass article (e.g., a vitreous glass sheet) that is formed directlyfrom the melt or derived from a continuous solidified melt, and thus, isnot, and does not contain, compacted or discrete glass-powder particles(e.g., sulfur containing glass-powder particles), and therefore thevitreous glass phase (or more simply vitreous phase) or vitreous glasslayer (or more simply vitreous layer) or vitreous glass article (or moresimply vitreous article) is also entirely devoid of compactedglass-powder inter-particle boundaries. Moreover, without intending tobe limited by theory it is believed that the ability of the solidelectrolyte sheet of the present disclosure to resist and preferablyprevent dendritic through penetration in a lithium battery cell is basedon its fabrication as a vitreous glass with liquid-like surfaces, bywhich it is meant a smooth amorphous surface, as resulting from theaction of surface tension on a quiescent liquid.

In various embodiments, the freestanding solid electrolyte of thepresent disclosure is a vitreous monolithic glass sheet havingliquid-like surfaces, wherein the continuous Li ion conducting amorphousmaterial phase is a vitreous glass present in an uninterrupted fashionthroughout the entirety of the solid electrolyte, and therewitheffectively provides a continuous amorphous expanse of vitreous glass(i.e., a vitreous glass matrix) that is pervasive of the entire sheet.

When referring to the freestanding solid electrolyte sheet as a“vitreous monolith,” or as a “vitreous monolithic sheet,” it is meant by“monolith or monolithic” that the freestanding sheet is of substantiallyuniform glass composition. Accordingly, the vitreous monolithic sheet isnot a laminate or multi-layer of two or more vitreous layers ofdifferent composition or microstructure, such as a physical or chemicalvapor deposited layer (i.e., CVD or PVD) requiring a substrate for itsformation and mere existence, and therefore not freestanding nor amonolith.

The vitreous solid electrolyte glass sheet of this disclosure addressesnumerous shortcomings of pressed/hot-pressed sulfide glass powdercompacts, polycrystalline ceramic membranes (e.g., garnets and LTP/LGP),and solid polymer electrolyte films (e.g., PEO-like).

For example, powder compaction is fraught with mechanical andelectrochemical complications related to surface flaws, inter-particleboundaries and an undue density of void-like defects, which act asstress concentrators that limit strength, thwart flexibility and serveas Li dendrite initiators and facile pathways for dendritic shorting.And while simultaneous heating and pressing (i.e., hot pressing) at highpressures for extended times can be useful for improving inter-particlecohesion, it adds a costly additional step that complicates processingand does not adequately address surface flaws related to dendriteinitiation, as expounded on in some detail herein below. Moreover,powder compaction, while suitable for making small pressed pellets, is abatch process that is not scalable, and cannot be used to make longflexible sheets of glass.

Mechanical failure of any glass (e.g., window glass) will occur when thestress and defect size reach a critical combination. The reliability istherefore statistical, but nonetheless related to the largest sizedflaws on the surface. In contrast, small shallow flaws are perceived asless important, since the underlying mechanical strength of the sheet islargely unaffected by their existence. When shallow flaws are small innumber density, or even singular, their very existence is generallyconsidered insignificant from a practical perspective.

At practical current densities however, a shallow flaw at an otherwiseliquid-like surface can be prohibitive for realizing a dendriteresistant solid electrolyte glass sheet, if the flaw depth is beyond athreshold size for dendrite initiation. In a lithium metal battery cell,wherein a vitreous solid electrolyte sheet is in contact with a solid Limetal anode, a flaw extending beyond a threshold depth can create ahighly localized hot spot for current focusing, which can lead to veryhigh local current densities and dendritic penetration of Li metal intothe sheet during cell charging, even for electrolytes with elasticmoduli well above 20 GPa.

Considerations for determining the threshold flaw depth and the generalfunctional relationship between the local and nominal current densitiesis described in more detail herein below. Preferably, the deepest flawextension into the sheet is less than 1% of the sheet thickness, andpreferably less than 0.1%, and generally no more than 5 μm. For example,the deepest flaw extension in a 100 μm thick sheet should be less than 1μm, and more preferably less than 0.1 μm; and for a 50 μm thick sheet itshould be less than 0.5 μm, and preferably less than 0.05 μm.

Considering the sensitivity of dendrite initiation to the presence ofshallow flaws, processing methods which can yield pristine surfaces aredesirable, and special care should be given to minimize contact damageduring handling and downstream processing of cell components and cells.

In various embodiments, to achieve a liquid like surface of exceptionalsmoothness, or to ensure sufficient surface quality commensurate with aspecified degree of flexibility or dendrite impenetrability, the instantsolid electrolyte sheet may be subjected to a grind and/or polish.Preferably, the need to polish or grind is circumvented by fabricating avitreous glass sheet having naturally formed high quality liquid-likesurfaces with a pre-determined uniform thickness in its virgin state asa solid.

By use of the term “virgin state as a solid” or more simply “virginstate” or even more simply “virgin” when referring to the instant solidelectrolyte sheet or its first and second principal side surfaces or thethickness of the sheet, it is meant to refer to the state of the solidelectrolyte sheet, state of its surfaces, and its thickness immediatelyupon the sheet's formation as a solid (i.e., immediately uponsolidification). More specifically the virgin state refers to the stateof the solid electrolyte sheet immediately upon reaching a temperaturebelow the lowest glass transition temperature (T_(g)) of the sheet,which may be determined by differential scanning calorimetry ordifferential thermal analysis. When referring to the solid electrolytesheet or a principal side surface in its virgin state as a solid, it(the sheet or surface) is sometimes more simply referred to as thevirgin solid electrolyte sheet or virgin principal side surface. Andwhen referring to a particular property of the virgin solid electrolytesheet, such as its thickness or surface roughness, the term virginthickness or virgin surface roughness may be used to refer to thethickness or roughness of the sheet/surface in its virgin state as asolid.

In various embodiments the first and second principal side surfaces ofthe sheet are untouched by an abrasive foreign surface, and, the desiredthickness and thickness uniformity is achieved in its virgin state as asolid. In various embodiments, the first and second principal sidesurfaces of the virgin solid electrolyte sheet are untouched by aforeign solid surface, and thus said surfaces are chemically andphysically pristine (i.e., untouched) in their virgin state—yieldingsignificant advantage as it pertains to surface smoothness, flaws, andcontaminants. The pristine surfaces, formed naturally in an inert fluidmedium (e.g., an inert gaseous environment such as Argon or Helium), arenot susceptible to surface imprints or other solid contact imperfectionsthat may accompany solidification in direct contact with a foreign solidbody surface. By use of the term “pristine” when referring to surfacesof the solid electrolyte sheet, it is meant that the referencedsurfaces, in their virgin state, are untouched by a foreign solidsurface.

In various embodiments, the as-solidified solid electrolyte sheet may bereferred to herein as a mother-sheet having a high quality centerportion, with uniform thickness and preferably smooth liquid-likesurfaces, and lower quality peripheral edge portions, which generallyextend along its lengthwise dimension, and are removed via a postsolidification process of cutting, preferably with a laser beam (i.e.,by laser cutting).

In order to achieve the high intrinsic Li ion conductivity as stipulatedabove for the inorganic amorphous material phase (i.e., ≥10⁻⁵ S/cm,preferably ≥10⁻⁴ S/cm, and more preferably ≥10⁻³ S/cm), sulfur-based Liion conducting glasses are, for this purpose, particularlysatisfactory—as the high polarizability of sulfur tends to enhance Liion mobility by weakening interactions with sulfur-glass formingskeletal ions.

By use of the term “sulfur-based” or “sulfide” when referring to theinorganic Li ion conducting amorphous material phase, and in particularwhen referring to the inorganic sulfide or sulfur-based glasses, it ismeant that the glass composition or glass system contains sulfur andmobile lithium as elemental constituents, and at least one moreelemental constituent (e.g., phosphorous, silicon, boron, arsenic andgermanium). The terms sulfur-based glass, sulfur-containing glass, andsulfide-glass are used interchangeably herein and in the claims.

In various embodiments the sulfur-based glass is composed of mainelemental constituents, as they are termed, except as additives orsecondary elemental constituents are indicated. The main elementalconstituents (including sulfur and lithium) have a mole percentage inthe glass that is greater than 20%, and the secondary elementalconstituents are present in the glass at a mole percentage of no morethan 20%, and typically no more than 10%. In various embodiments themain elemental constituents are sulfur, lithium, and one or moreselected from the group consisting of phosphorous, silicon, boron, andgermanium (e.g., phosphorous, boron and silicon).

For the avoidance of doubt, the term “sulfide-glass” or sulfur-basedglass is not meant to exclude oxygen or selenium as a constituentelement of the glass, and in embodiments oxygen may be one of the mainconstituent elements. When containing oxygen and sulfur, the sulfideglass is sometimes referred to herein as an oxy-sulfide glass tospecify, in the positive, that it contains both sulfur and oxygen. Invarious embodiments secondary constituent elements (e.g., silicon,oxygen, aluminum and phosphorous) may be incorporated in the glasscomposition for improving glass stability, increasing viscosity at theliquidus temperature and/or chemical/electrochemical compatibility withLi metal, even at the sacrifice of lower Li ion conductivity.

Highly conductive sulfide based Li ion conducting glasses are describedin the following documents, all of which are incorporated by referenceherein for their disclosure in connection with aspects of thisdisclosure: in Mercier R, Malugani J P, Fahys B, Robert G (1981) SolidState Ion 5:663; Pradel A, Ribes M (1986) Solid State Ion 18-19:351;Tatsumisago M, Hirai K, Minami T, Takada K, Kondo S (1993) J Ceram SocJpn 101:1315; Kanno R, Murayama M (2001) J Electrochem Soc 148:742;Murayama M, Sonoyama N, Yamada A, Kanno R (2004) Solid State Ion170:173; Hayashi A, Hama S, Minami T, Tatsumisago M (2003) ElectrochemCommun 5:111; Mizuno F, Hayashi A, Tadanaga K, Tatsumisago M (2005) AdvMater 17:918; Mizuno F, Hayashi A, Tadanaga K, Tatsumisago M (2006)Solid State Ion 177:2721; H. Wada, et al., “Preparation and IonicConductivity of New B2S₃—Li2S-Lil Glasses”, Materials Research Bulletin,February 1983, vol. 18, No. 2, pp. 189-193; Fuminori Mizuno, et al.,“All Solid-state Lithium Secondary Batteries Using High Lithium IonConducting Li₂S—P₂S₅ Glass-Ceramics”, Chemistry Letters 2002, No. 12,The Chemical Society of Japan, Dec. 5, 2002, pp. 1244-1245 (with 2 coverpages); Fuminori Mizuno, et al., “New, highly Ion-Conductive CrystalsPrecipitated from Li₂S—P₂S₅ Glasses”, Advanced Materials 2005, vol. 17,No. 7, Apr. 4, 2005, pp. 918-921; US Patent Pub. No.: 20070160911; andU.S. Pat. No. 8,012,631.

Li ion conducting sulfide glasses are advantageous in several respects.Firstly, their Li ion conductivity is high, and secondly they are softrelative to other inorganic materials, so when fabricated by mechanicalmilling, the powder particles may be pressure formed to a compact. As abulk glass, however, Li ion conducting sulfides have been previouslyperceived as prohibitively difficult to process into any sort of batteryserviceable cell component, and work in that area focused oncharacterizing compositions and examining conductivity in pellets madeby pulverizing the glass to a powder and pressing. Indeed, theperception that Li ion conducting sulfide glasses are highly prone tocrystallization on cooling and highly susceptible to devitrification onheating is understandable. Li ion conducting sulfide glasses areconsiderably more fragile than oxide glasses, and the high ionicconductivity is predicated on having large amounts of bond breaking Liions, which further destabilizes the glass. Perhaps this perception,combined with: i) their sensitivity to moisture and oxygen at hightemperature; and ii) the advent of relatively simple and direct lowtemperature mechanical milling approaches to making Li ion conductingsulfide glass powders, has effectively led the industry to moveexclusively in the direction of mechanically milling powders, followedby pressing powder compacts to fabricate components. Moreover, themechanical milling approach seemingly has all the advantages of a lowtemperature process without any disadvantage. Previously unrecognized,however, is that cold shaped or hot pressed sulfide based solidelectrolyte powder constructs are ultimately flawed bothelectrochemically and mechanically. Moreover, pressing dense powdercompacts is not a scalable process, and it is certainly not conducive tomaking long continuous sheets of glass, or a web.

It has been unexpectedly discovered that battery serviceablefreestanding vitreous sheets of sulfide based solid electrolyte glass,entirely devoid of powder inter-particle boundaries and residualimperfections thereof (such as surface voids and internal pores) can beformed in a different way. Li ion conducting sulfide glasses have beenfound to possess kinetic stability beyond that expected based onliterature reports, thermodynamic properties, and rheologicalcharacteristics, and it is postulated that causing, or allowing, thesulfide glass to flow may enhance stability, and thereby improve glassformability as well as stability against crystallization, and, inparticular, facilitate drawing the glass from a fluid or liquid state(e.g., drawing the sulfide glass from a preform or pulling on it as amolten sheet). In this way, a battery serviceable freestanding vitreoussheet of sulfide based Li ion conductive solid electrolyte glass,preferably substantially impenetrable to Li dendrites, and entirelydevoid of powder inter-particle boundaries and residual imperfectionsderived from pressing a powder compact, may be formed.

In another aspect, this disclosure is directed to methods of making athin dense wall structure of an inorganic Li ion conducting amorphousmaterial phase, and, in particular embodiments, the wall structure is athin vitreous sheet of sulfide-based Li ion conducting glass, and invarious embodiments formed as a continuous web having substantiallyparallel lengthwise edges, and sufficient flexibility to be wound into acontinuous roll without fracture.

In various embodiments the methods of this disclosure involve forming aLi ion conductive sulfide based glass material into a thin inorganicfluid sheet of unbroken continuity, and causing or allowing the fluidsheet to flow along its lengthwise dimension prior to solidifying (i.e.,the flowing fluid sheet a fluid stream of glass). In variousembodiments, the fluid stream of unbroken continuity retainssubstantially parallel lengthwise edges as it flows, and the stream hasat least high quality center portion that is thin and preferably ofsubstantially uniform thickness ≤500 μm.

By use of the term “fluid sheet” when referring to methods of making ofthe instant solid electrolyte sheets it refers to the sheet, or asection thereof, at a temperature that is greater than the glasstransition temperature (T_(g)) of the material from which the sheet ismade, and typically significantly higher than T_(g). By use of the term“fluid stream” it is meant the fluid sheet flowing, and typically causedto flow by gravity and/or an external force, such as motorized pullingrods or rollers. In some embodiments, the fluid stream of unbrokencontinuity is formed from a liquid melt of a sulfur-containing glass, ator above the liquidus temperature (T_(liq.)). In other embodiments thefluid stream of unbroken continuity is formed by heating a solid preformof sulfur-containing glass to a temperature at which it deforms underits own weight (e.g., above the softening temperature of the glasspreform).

Recognizing the benefit of perfecting the sulfide glass into a vitreousmonolith as opposed to a powder construct, methods and modifiedsulfur-based glass compositions that are less prone to crystallizationand/or have higher melt viscosities but still retain a requisite levelof Li ion conductivity (>10⁻⁵ S/cm) have been developed. In particular,methods for increasing the glass stability factor and/or Hrubyparameter, including increasing the amount of oxygen in the glass,increasing the oxygen to sulfur mole ratio, increasing the amount ofoxide network former in the glass, increasing the ratio of oxide networkformer to sulfide network former, incorporating silicon for networkforming, decreasing the amount of bond breaking lithium ions, tuning thecomposition of the base sulfide glass to have more than 4 main elementalconstituents (e.g., 5 main elemental constituents: S, Li, B, P, and O)or more than 5 main elemental constituents (e.g., 6 main elementalconstituents: S, Li, Si, B, P, and O) and combinations thereof aredescribed. In addition, additives to the base glass are alsocontemplated for use herein as devitrifying agents and crystallizationinhibitors.

Moreover, while apparently counterintuitive to decrease the Li ionconductivity of a glass that is specifically intended for use in abattery cell as a Li ion conductor, in various embodiments this is theapproach contemplated herein for making and improving properties of thevitreous solid electrolyte sheets of this disclosure. Accordingly, invarious embodiments the composition of the glass is adjusted to enhancethermal properties at the sacrifice of reduced conductivity.

A number of terms are used in the description for discussing the thermalproperties of the glass. {T_(x)−T_(g)} is the difference between theonset of crystallization (T_(x)) and the glass transition temperature(T_(g)), and is also referred to herein as the glass stability factor;{T_(n)−T_(x)} is the difference between the temperature at which theglass is drawn (T_(n)) and the onset of crystallization. The liquidustemperature is (Li_(n)), and the viscosity of the glass at T_(liq), isthe liquidus viscosity. The melting temperature of the glass is (T_(m)).The strain temperature is the temperature at which the viscosity of theglass is approximately 10^(14.6) poise, and stresses may be relieved inhours. The annealing temperature is the temperature at which theviscosity is approximately 10^(13.4) poise, and stresses in a glass maybe relieved in less than 1 hour or minutes. And finally, the softeningtemperature is defined as the temperature at which the glass hasviscosity of ˜10^(7.6) poise. The glass is usually suitable for drawingat or above this temperature.

Several techniques exist for the measurement of these characteristictemperatures. Differential scanning calorimetry (DSC) and differentialthermal analysis (DTA) are the most common. Generally, a largeseparation between T_(x) and T_(g) (i.e., a large glass stabilityfactor) is desirable for drawing glass.

Another method of determining or estimating glass stability is throughthe Hruby parameter (H_(r) parameter), as given by the followingequation:

${Hr} = \frac{{Tx} - {Tg}}{{Tm} - {Tc}}$

A high value of H_(r) suggests high glass stability, and the larger, themore stable the glass against crystallization. For example, a glasshaving H_(r)<1, is generally highly prone to crystallization andconsidered unstable.

In another aspect, the vitreous solid electrolyte sheet of Li ionconducting sulfide glass is manufactured in the form of a standalonevitreous web of glass. In various embodiments multiple discrete solidelectrolyte sheets or ribbons are cut to size from the vitreous Li ionconducting glass web. In various embodiments the vitreous web issufficiently thin, long and robust when flexed that it can be woundwithout fracture. In various embodiments, the web is wound about a spoolto yield a continuous supply roll, or source roll, for storage,transportation, and/or R₂R manufacture of downstream cell components andbattery cells. When referring to the rolled web (e.g., rolled about aspool), the term coil is sometimes used herein interchangeably with theterm roll.

In other aspects the disclosure provides battery cell componentscomposed of the solid electrolyte sheets of this disclosure, includingelectrode sub-assemblies and electrode assemblies (e.g., positive andnegative electrode assemblies), including sealed fully solid-state Limetal electrode assemblies, encapsulated electrode assemblies, andelectrode assemblies having an unconstrained backplane architecture.

In yet other aspects the disclosure provides web laminates wherein thevitreous Li ion conducting glass web serves as a substrate for theformation of an electrode sub-assembly web and an electrode assemblyweb.

And in other aspects there are provided herein lithium battery cellscomprising the solid electrolyte sheets and cell components of thisdisclosure, including lithium ion cells, lithium metal battery cells,hybrid lithium battery cells, solid-state lithium battery cells, andcells having a common liquid electrolyte.

With reference to FIGS. 1A-D and FIGS. 2A-B there are illustrated Li ionconductive thin solid electrolyte wall structures 100 and 200A-B inaccordance with various embodiments of this disclosure (i.e., solidelectrolyte wall structures), as described above and herein below.Effectively, the solid electrolyte wall structure, as it is referred toherein, is a dense freestanding and substantially amorphous inorganiclayer that is highly conductive of Li ions and composed of a continuousinorganic and amorphous material phase having intrinsic room temperatureLi ion conductivity ≥10⁻⁵ S/cm, preferably ≥10⁻⁴ S/cm, and morepreferably ≥10⁻³ S/cm. In various embodiments, the wall structure is inthe form of a long sheet or ribbon 100 (see FIGS. 1A-D). However, inother embodiments the solid electrolyte layer is articulated to yield awall structure in the form of a hollow prism-like receptacle, as shownin FIGS. 2A-B.

Notably, the continuous nature of the amorphous material phase isuninterrupted and thus gives rise to a bulk microstructure that isdevoid of interconnected void-like pathways (e.g., grain boundaries orparticle boundaries), which, if otherwise present, would allow facilepenetration of lithium metal dendrites across the thickness of the layer(i.e., the wall). Preferably, the wall structure bears a liquid-likesurface that renders it substantially impenetrable to lithium metaldendrites, and thus, when incorporated as a Li ion-conducting componentin a solid electrolyte separator (or as the separator itself), the wallstructure, entirely inorganic, is enabling for the realization of areliable and safe lithium metal secondary battery.

With reference to FIGS. 1A-D, solid electrolyte wall structure 100 is afreestanding substantially amorphous and inorganic Li ion conductingsolid electrolyte sheet (e.g., a long relatively narrow ribbon) havingfirst and second opposing principal sides (101A and 101B respectively)and associated principal side surfaces, substantially parallellengthwise edges, length dimension (1), width dimension (w), averagethickness dimension (t), and an area aspect ratio defined as (l/w).Solid electrolyte sheet 100 is highly conductive of Li ions, and has Liion conductivity, as measured between its first and second principalside surfaces, of at least 10⁻⁵ S/cm, preferably at least 10⁻⁴ S/cm, andmore preferably at least 10⁻³ S/cm.

In various embodiments sheet 100 is thin with substantially uniformthickness (t), as measured between its first and second principal sides.By thin it is meant no thicker than about 500 μm, preferably no thickerthan 250 μm, more preferably no thicker than 100 μm, and even morepreferably no thicker than 50 μm. In various embodiments the sheet hasuniform thickness in the range of 5≤t≤500 μm. In particular embodimentsit has a uniform thickness in the range of: 5≤t<10 μm; 10≤t<30 μm;30≤t<50 μm; 50≤t<100 μm; 100≤t<250 μm; and 250≤t≤500 μm. Thicker solidelectrolyte sheets, greater than 500 μm, are also contemplated for someapplications, and may be of particular utility for grid storage backup,which does not necessarily require flexibility or high power density(Wh/l). For example, thick sheets having a uniform thickness in therange of 500 μm<t≤2 mm are contemplated for this purpose. Preferably,the specified thickness and thickness uniformity of the solidelectrolyte sheet is achieved in its virgin state as a solid, and bythis expedient benefit is gained in terms of cost, scaling and surfacequality.

In various embodiments sheet 100 is large and readily scalable in size.In various embodiments solid electrolyte sheet 100 is greater than 10cm², greater than 25 cm², greater than 50 cm², greater than 100 cm², orgreater than 1000 cm². In various embodiments, freestanding solidelectrolyte sheet 100 is long with substantially parallel lengthwiseedges and a length dimension ≥10 cm, ≥20 cm, ≥30 cm, ≥50 cm, and ≥100cm. In various embodiments, the width dimension of the long sheet isbetween 1 to 5 cm (e.g., about 1 cm, about 2 cm, about 3 cm, about 4 cm,or about 5 cm wide) or between 5 to 10 cm (e.g., about 5 cm, or about 6cm, or about 7 cm, or about 8 cm or about 9 cm, or about 10 cm wide). Invarious embodiments the solid electrolyte sheet is in the shape of athin ribbon of uniform thickness; for instance, the ribbon having length(l)≥10 cm, width (w) between 1 to 10 cm, and area aspect ratio (l/w)≥5,(l/w)≥10, (l/w)≥20. For example, the solid electrolyte sheet may have anarea aspect ratio in the range of 5 to 20. The sheet may be cut intopieces of any suitable size for use, such as a separator in into abattery cell or component.

Sheet 100 should have low area specific resistance (ASR), as measuredbetween its first and second principal side surfaces. In accordance withthe disclosure, the area specific resistance is sufficiently low to bebattery serviceable, and substantially uniform across the entirety ofthe sheet. Preferably the sheet has area specific resistance <200 Ω-cm²,more preferably <100 Ω-cm², even more preferably <50 Ω-cm², and yet evenmore preferably <10 Ω-cm². When measured at various local points, theASR preferably varies by less than 20% from the average value, morepreferably the variance is less than 10%, and even more preferably lessthan 5%. For instance, if the ASR is about 100 Ω-cm², the arearesistance at localized positions along the sheet is preferably between80 to 120 Ω-cm², and more preferably between 90 to 110 Ω-cm², and yeteven more preferably between 95 to 105 Ω-cm². To achieve such low ASR,the solid electrolyte sheets of this disclosure are highly conductive ofLi ions, with conductivity of at least 10⁻⁵ S/cm, preferably ≥10⁻⁴ S/cmand even more preferably ≥10⁻³ S/cm.

With particular reference to FIGS. 1B-C, freestanding and substantiallyamorphous inorganic solid electrolyte sheet 100 is flexible, andpreferably sufficiently robust when flexed that it can be rolled on adrum or spool for storage and/or transportation, and therefore suitablefor roll processing, including roll-to-roll (R₂R) manufacturing (i.e.,it is R₂R suitable), or for winding or folding into a battery cell.

Flexibility of sheet 100 is dependent upon its Young's modulus,thickness, and surface quality; and, in particular, the quantity andsize of spurious edge cracks which may be present on its first or secondprincipal side surfaces 101A/101B. The flexibility of sheet 100 may becharacterized by its bending-radius (r), when the sheet is caused tobend without breaking. The bending-radius is defined as the minimumradius of the arc at the bending position where the sheet reachesmaximum deflection before kinking or damaging or breaking. In variousembodiments sheet 100 is sufficiently flexible to enable R₂R processingand preferably allow its use as a separator in a battery cell of woundor folded construction. For example, sheet 100 having a bending-radius≤100 cm, preferably ≤50 cm, more preferably ≤10 cm, even more preferably≤5 cm, yet even more preferably ≤2.5 cm. Or to enable its use in awound/folded battery cell, the sheet having a bending-radius ≤2.5 cm,preferably ≤1 cm, more preferably ≤0.5 cm, even more preferably ≤0.25cm, and yet even more preferably ≤0.1 cm.

Flaw location is also important, as the edges generally contain largerflaws. In various embodiments, if the solid electrolyte sheet is cut, itmay be important to edge finish (e.g., by fire polishing). To beflexible enough to achieve a suitable bending-radius for rollmanufacturing or battery cell winding, care must be taken in handlingthe solid electrolyte sheet to ensure that edge flaws are kept to aminimum. The threshold edge flaw size allowable depends on the thicknessof the sheet (t), Young's modulus (E), fracture toughness (Kit) and thedesired bending-radius (r), which, for the threshold crack size, may beascertained from 4r²(K_(lc))²/(πE²d²). In various embodiments, theYoung's modulus (E) of sheet 100 is less than 90 GPa, and edgecracks >10 μm should be avoided. Preferably solid electrolyte sheet 100is devoid of any edge crack >10 μm, and preferably >5 μm, morepreferably devoid of edge cracks >3 μm or >2 μm, and even morepreferably devoid of edge cracks >1 um.

In accordance with the present disclosure, the instant solid electrolytesheets are battery serviceable, and in various embodiments suitable foruse as a continuous solid electrolyte separator in a variety of lithiumbattery cells, including cells of wound or stacked construction andmoderate to high capacity (1 Ah-100 Ah).

In various embodiments freestanding sheet 100 is of battery serviceablesize, shape, flexibility and thickness to serve as a continuous solidelectrolyte separator in a battery cell defined by one or more of: i) awound, folded or stacked construction; ii) a square, circular,rectangular or cylindrical footprint; iii) a rated cell capacity in therange of 250 mAh-500 mAh; 500 mAh-1 Ah, 1 Ah-5 Ah, 5 Ah-10 Ah, 10 Ah-20Ah, 20 Ah-50 Ah, and 50 Ah-100 Ah; and iv) an area electrode capacitybetween 0.5 mAh/cm²-10 mAh/cm². By continuous solid electrolyteseparator it is meant that the sheet provides a continuous separatorbetween positive and negative electroactive layers of a cell in which it(sheet 100) is disposed.

In a particular embodiment, sheet 100 is battery serviceable as acontinuous solid electrolyte separator in a lithium battery cell ofwound or folded construction, and thus solid electrolyte sheet 100 hassubstantially parallel lengthwise edges and sufficient flexibility to bewound, typically around a mandrel, or folded, with a bending-radius ≤2.5cm, preferably ≤1 cm, more preferably ≤0.25 cm, and yet even morepreferably ≤0.1 cm.

In another particular embodiment solid electrolyte sheet 100 is batteryserviceable as a continuous solid electrolyte separator in a lithiumbattery cell having a rated capacity in the range of 250 mAh-500 mAh andan area electrode capacity between 0.5-5 mAh/cm², and thus thecontinuous area of sheet 100 is in the range of 25 cm²-1000 cm², andmore typically in the range of about 125 cm²-1000 cm² or about 250cm²-1000 cm². For example, sheet 100 having a width in the range of 0.5cm-10 cm (e.g., about 1 cm-5 cm) and a length in the range of 20 cm-100cm (e.g., about 50 cm to 100 cm).

In another particular embodiment continuous solid electrolyte sheet 100is battery serviceable as a continuous separator layer in a lithiumbattery cell having a rated capacity in the range of 500 mAh-1 Ah and anarea electrode capacity between 1-5 mAh/cm², and thus the continuousarea of sheet 100 is in the range of 100 cm²-1000 cm². For example,sheet 100 having a width in the range of 1 cm-10 cm (e.g., about 2 cm-5cm) and a length in the range of 50 cm-500 cm.

In yet another particular embodiment sheet 100 is battery serviceable asa continuous separator layer in a lithium battery cell having a ratedcapacity in the range of 1 Ah-5 Ah and an area electrode capacitybetween 1-5 mAh/cm², and thus the continuous area of sheet 100 is in therange of 200 cm²-5000 cm². For example, sheet 100 having a width in therange of 1 cm-10 cm (e.g., about 5 cm-10 cm) and a length in the rangeof 100 cm-1000 cm.

In still yet another particular embodiment sheet 100 is batteryserviceable as a continuous separator layer in a lithium battery cellhaving a rated capacity in the range of 5 Ah-10 Ah and an area electrodecapacity between 1-5 mAh/cm², and thus the continuous area of sheet 100is in the range of 1000 cm²-10000 cm². For example, sheet 100 having awidth in the range of 5 cm-10 cm and a length in the range of 100cm-2000 cm.

In various embodiments, sheet 100 is battery serviceable for use as acontinuous solid electrolyte separator in a lithium battery cell ofdefined rectangular footprint, including the cell having a width in therange of about 0.5 cm to 10 cm, and a rated cell capacity (Ah) and areaelectrode capacity (mAh/cm²) as stipulated above for the variousparticular embodiments. For instance, sheet 100 having length dimension≥10 cm, ≥20 cm, ≥30 cm, ≥50 cm, and in some embodiments ≥100 cm. Forexample, a width dimension between about 1 cm to 5 cm, and a lengthdimension between 10 cm to 50 cm (e.g., the width about 5 cm and thelength about 20 cm-50 cm) or a width dimension of 5 cm to 10 cm and alength dimension of 50 cm to 100 cm.

The afore described battery serviceable characteristics (e.g., length,area, aspect ratio, uniform thickness, and flexibility) are not trivialfor a vitreous sulfide-based solid electrolyte glass sheet, and suchsheets should be held in stark contrast to that of Li ion conductingsulfide glass flakes made by rapid twin roller quenching, mechanicallymilled or pulverized glass powders, and unwieldy melt/quenched blobswhich are generally irregularly shaped pieces of glass having virtuallyno dimensional or geometric shape tolerances, and therefore ofinapplicable size, shape and thickness to be battery serviceable. Incontradistinction, the thin vitreous solid electrolyte sheets of thisdisclosure are manufacturably reproducible, scalable and of batteryserviceable size, shape, and uniform thickness.

Continuing with reference to FIGS. 1A-D, solid electrolyte sheet 100 isfreestanding and not surrounded or supported by an external substrate orstructure that serves as a support structure, such as a supportingmaterial layer, dense or porous. Accordingly, freestanding solidelectrolyte sheet 100 is a self-supporting layer that is not only devoidof a supporting electrode structure (e.g., a positive electrode layer),it is also devoid of inert supporting material layers, such as porous ordense carrier or release layers. Accordingly, in various embodiments theinstant freestanding sulfide based solid electrolyte sheet issubstrate-less, and by this it is meant to include the absence of aninterior substrate within the bulk of sheet 100 (i.e., an internalsupporting structure), as well as the absence of an exterior substratecovering principal side surfaces 101A or 101B. Moreover, solidelectrolyte sheet 100 is completely inorganic, and therefore does notcontain any organic polymeric binder material, or the like.

In various embodiments, solid electrolyte sheet 100 is cut-to-size fromthe high quality center portion of a mother-sheet. For instance, withreference to FIGS. 1 E-F, there is illustrated a mother-sheet ofvitreous Li ion conducting sulfur-containing glass made, for instance,by melt drawing or preform drawing. Mother-sheet 100M may becharacterized as having a high quality center portion 105 and lowerquality edge portions 107 which are removed by laser cutting. To ensureutmost quality, peripheral portions of the high quality center region105 x are generally removed during the lengthwise cutting procedure.

Preferably, the high quality center portion 105 accounts for at least20% of the mother-sheet's footprint/area (e.g., at least 30%, at least40%, at least 50%, at least 60%, at least 70%, at least 80%, or at least90%). Preferably the mother-sheet is of sufficient quality that itrequires minimal or no edge removal in order to yield a solidelectrolyte sheet with uniform thickness and/or smooth surfaces.

Preferably the high quality center portion of mother-sheet 100M hassufficient surface quality to circumvent the need to perform apost-solidification polishing step. For instance, in variousembodiments, the major opposing surfaces of the high quality centerportion of mother-sheet 100M has an average surface roughness R_(a)<1.0μm, preferably <0.5 μm, more preferably R_(a)<0.2 μm, even morepreferably R_(a)<0.1 μm, yet even more preferably R_(a)≤0.05 μm, orR_(a)≤0.05 μm, or R_(a)≤0.01 μm. In addition to high surface quality,the high quality center portion is preferably of thickness and thicknessuniformity to circumvent the need to grind down its surfaces, or moregenerally remove material from the surfaces in order to achieve adesired thickness and/or thickness uniformity. In various embodiments,the surfaces of the high quality center portion of mother-sheet 109 arechemically and physically pristine in their virgin state, and thusuntouched by a foreign solid surface upon solidifying.

In accordance with the foregoing, in various embodiments, thecut-to-size virgin solid electrolyte sheet, or the high quality centerportion of the as-solidified mother sheet, or the entire mother sheetitself, possesses one or more of the following characteristics: i) athin uniform thickness ≤500 μm (e.g., ≤100 μm); ii) pristine liquid-likefirst and second principal side surfaces; iii) substantial flatness; iv)average surface roughness R_(a)<1 μm; v) sufficient surface quality andthinness to enable flexibility commensurate with winding the solidelectrolyte sheet to a radius of curvature ≤10 cm without fracturing;pristine first and second principal side surfaces having opticalquality.

With reference to FIG. 1G there is illustrated an edge protectedelectrolyte sheet 101G composed of sheet 100 fitted with electricallyinsulating edge-protector element(s) 105, which, in addition tosafeguarding against physical damage to an edge, provide ancillarybenefit as it pertains to mechanical strength and wind-ability,including embodiments wherein the edge-protector elements are engineeredas a spacer to prevent contact between adjacent surfaces when it (thesheet) is wound as a continuous roll of solid electrolyte sheet (e.g.,as a supply or source roll). In various embodiments the edge-protectorelements may be a polymer film, such as a tape adhered to and coveringthe edges, or a rigid square-like polymeric bracket snug fit to theedges; the edge-protector element(s) may be removable or permanent.

Notwithstanding the freestanding nature of solid electrolyte sheet 100,this disclosure contemplates that freestanding and substrate-less sheet100 may have on one or both of its principal side surfaces a materiallayer, such as a coating or thin film, that serves, in part or in whole,to protect one or both principal surfaces, but it (the protectivematerial coating/film) is not relied upon to support the sheet. Indeed,quite the opposite, the sheet in such instances is generally relied uponto serve as a substrate support for the surface protecting materiallayer. For instance, as illustrated in FIG. 1H and described in moredetail herein below, in various embodiments freestanding solidelectrolyte sheet 100 may be subjected to a coating process whereby thefirst and/or second material side surface 101A and/or 101B is coatedwith one or more thin material layers 110 to form what is termed hereinan electrode sub-assembly 101H, which is effectively sheet 100 coated bymaterial layer 110. In various embodiments layer 110 is a tie-layer thatprotects surface 101A while also providing a reactive/bonding layer formaking intimate contact with Li metal on contact, or layer 110 may be acurrent collector coating, or layer 110 may be a multi-layer of atie-layer and a current collecting layer. Generally, material layer(s)110 of electrode sub-assembly 101H are not Li ion conducting layers(i.e., σ^(Li)<10⁻⁹ S/cm). However, the disclosure does contemplateotherwise, and in such instances, the Li ion-conducting layer is coateddirectly onto the first and/or second principal side surface (101Aand/or 101B), optionally followed by a tie-layer and/or currentcollector coating. Accordingly, in various embodiments, the instantfreestanding solid electrolyte sheet serves as a substrate for making abattery cell or an electrode assembly, and thereby, when used as such,sheet 100 is sometimes referred to herein as a substrate-sheet. Forinstance, the first or second principal side surface may be coated witha thin Li ion conducting glass film for improved chemical compatibilityin contact with Li metal or battery cell components (e.g., a sulfideglass of different composition or a very thin lithium oxide, lithiumphosphate or lithium oxynitride glass film). Indeed, the freestandingnature of the vitreous solid electrolyte sheet combined with its smoothliquid-like surfaces, provides significant advantage for creating andutilizing dense exceptionally thin surface films (e.g., <1 μm thick, or<0.5 μm thick, or <0.1 μm thick), and so enabling of glassy inorganicmaterials with intrinsic Li ion conductivity less than 10⁻⁶ S/cm.

Continuing with reference to FIGS. 1A-D, standalone solid electrolytesheet 100 is clearly devoid of an exterior substrate, as its principalside surfaces are directly exposed or directly exposable to the adjacentambient gaseous environment. For instance, in various embodimentssubstrate-less sheet 100 (flexible or otherwise) may be handle-able bygloved hand or apparatus, and remain intact when placed in a suspendedstate (e.g., when dangled by holding the sheet along an edge).Standalone and freestanding sheet 100 is not a PVD or CVD layer thatrequires a substrate for its formation and existence. In fact, invarious embodiments substrate-less sheet 100 may be fabricated in theabsence of a substrate or even in the absence of a contacting surface(such as a mold surface). In such embodiments, solid electrolyte sheet100 is formed with both first and second principal side surfaces fullyexposed to the ambient gaseous environment (inert). And by thisexpedient, the sheet so formed, is absent imperfections, imprints,chemical reaction products, and contaminants that would otherwise appearon or nearby its surface if the sheet were solidified in direct contactwith a foreign solid body surface.

In various embodiments sheet 100 is fabricated to ensure that it issubstantially impervious to liquids that it may contact during operationof a device in which it is incorporated, such as a liquid electrolyte ina battery cell of the instant disclosure. In such embodiments sheet 100should be free (i.e., devoid) of through porosity including pinholes ordefects which would otherwise allow a liquid electrolyte to seep throughthe sheet from the first to the second principal side, or vice versa. Inother embodiments liquid impermeability is not a requisite property ofthe solid electrolyte sheet, albeit perhaps a desirable one; forinstance, sheet 100 incorporated in a fully solid-state battery cell asa solid electrolyte separator.

With reference to FIGS. 1A-D, in various embodiments at least firstprincipal side surface 101A is chemically compatible in direct contactwith lithium metal, and in some embodiments both first and secondprincipal side surfaces 101A/101B are chemically compatible in directcontact with lithium metal. However, the disclosure is not limited assuch, and in some embodiments the first and/or second principal sidesurfaces may be chemically incompatible in direct contact with lithiummetal. For instance, solid electrolyte sheet 100 may be employed as asolid electrolyte separator disposed between a pair of porous separatorlayers or gel layers impregnated with a liquid electrolyte, or solidelectrolyte sheet 100 may be coated (on one or both principal sidesurfaces) with a glassy Li ion conducting film to form a solid-stateprotective membrane architecture as described in more detail hereinbelow.

In alternative embodiments, as illustrated in FIGS. 2A-B, thefreestanding substantially amorphous and inorganic Li ion conductingsolid electrolyte layer, as described above, provides a wall structurein the form of a hollow prismatic receptacle 200A-B, having interior andexterior surfaces 201A and 201B, length dimension (l), width dimension(w) and layer/wall thickness dimension (t). When a prismatic receptacle,the two parallel end portions (203A/203B) are typically open (as shown),but the disclosure is not limited as such, and it is contemplated thatthe wall structure may have a closed end defined by the solidelectrolyte layer in contiguity with the receptacle portion. Moreover,hollow prism 200A-B may be further characterized as having major andminor opposing lateral wall portions, specifically major opposing wallportions 205 a and 205 b, and minor opposing wall portions 207 a and 207b. In a particular embodiment wall structure 200A is a hollow prism inthe form of an open-ended elliptical cylinder. In another embodiment thewall structure is a hollow rectangular prism 200B, optionally havingexterior and/or interior corners substantially rounded as shown in FIG.2B. Moreover, the interior volume (V) is defined by the interior gap(g), width dimension (w) and length dimension (l), and when elliptical,the interior gap is defined as the distance across the semi-minor axisof the elliptically shaped end portion.

With reference to FIG. 3A, in various embodiments the solid electrolytesheet may be of sufficient flexibility, length and manufacturability tobe fabricated as a continuous web of vitreous inorganic Li ionconducting sulfide glass 100W, having a length typically greater than 50cm, and preferably greater than 100 cm, and even more preferably greaterthan 1000 cm long. In various embodiments, glass web 100W serves a solidelectrolyte substrate-sheet for the formation of downstream battery cellcomponents, including electrode subassemblies, electrode assemblies, andbattery cells of this disclosure.

As illustrated in FIG. 3A, in various embodiments web 100W issufficiently flexible that it may be formed into a continuous roll 100Rwithout fracture, and typically wound on a support spool 301 for storageand/or transportation. Preferably continuous web 100W has bending-radius≤100 cm, and preferably ≤50 cm, more preferably ≤10 cm, even morepreferably ≤5 cm, and yet even more preferably ≤2.5 cm, and thus capableof being wound as such without fracture. In various embodiments thespool or drum has a diameter in the range of 100 cm-200 cm; or 50 cm to100 cm; or 20 to 50 cm; or 10 cm to 20 cm; or 5 cm to 10 cm; or 2.5 cmto 5 cm. In various embodiments continuous roll 100R serves as a supplyroll or a source roll for R₂R manufacture or roll-to-sheet processing ofdownstream battery cell components and battery cells.

As illustrated in FIG. 3B, in various embodiments, multiple discretesolid electrolyte sheets 100Z (e.g., a stack of solid electrolytesheets) may be excised (i.e., cut to size) from Li ion conducting glassweb 100W. The sheet may be cut into pieces of any suitable size for use,such as a separator in into a battery cell or component. In variousembodiments, web 100W yields at least 5 discrete solid electrolytesheets having length of at least 10 cm, preferably at least 10 suchsheets, more preferably at least 50 such sheets, and even morepreferably at least 100 such sheets.

In various embodiments, to facilitate winding, storage and/or use of asupporting spool, a protective material interleave (not shown) may bedisposed between adjacent layers of the source roll in order to preventthe opposing web surfaces from contacting each other. Generally, theprotective interleave is not a lithium ion conductor. In variousembodiments the interleave may be a porous polymer layer (e.g.,micro-porous) or a dry swellable polymer layer (i.e., a dry gellablepolymer layer), suitable to serve as both interleave in the source rolland as a porous or gel separator component in a battery cell.

In accordance with the disclosure, the continuous Li ion conductingamorphous material phase has room temperature intrinsic Li ionconductivity ≥10⁻⁵ S/cm, preferably ≥10⁻⁴ S/cm, and more preferably≥10⁻³ S/cm. To achieve this level of conductivity in an inorganicamorphous material phase, sulfide based Li ion conducting glasses areparticularly suitable (i.e., sulfur-containing glasses). Withoutintending to be limited by theory, compared to oxygen, sulfur is foundto be a highly desirable element of the material phase. Sulfur isgenerally more polarizable than oxygen, and this tends to weaken theinteraction between glass forming skeletal ions and mobile lithium ions,which in turn enhances lithium ion mobility and increases associatedionic conductivity. Accordingly, in various embodiments the materialphase has a glass skeleton composed in part of sulfur and through whichLi ions move. Without intending to be limited by theory, sulfur mayserve several roles, including cross-linking sulfur that forms the glassstructure and non-crosslinking sulfur that combines terminally withmobile Li ions.

Accordingly, in various embodiments the continuous amorphous materialphase of solid electrolyte sheet 100 is an inorganic sulfide based glasscomprising S (sulfur) as a constituent element, Li (lithium) as aconstituent element and further comprising one or more constituentelements selected from the group consisting of P (phosphorous), B(boron), Al (aluminum), Ge (germanium), Se (selenium), As (arsenic), O(oxygen) and Si (silicon).

In embodiments, the sulfide-based solid electrolyte glass comprises O(oxygen) as a constituent element (e.g., typically as a secondaryconstituent element). In other embodiments, the amorphous sulfide glassis a non-oxide, and thus substantially devoid of oxygen as a constituentelement. Typically the mol % of Li in the glass is significant, and inparticular embodiments the mole percent of Li in the glass is at least10 mol %, and more typically at least 20 mol % or at least 30 mol %; insome embodiments it is contemplated that the mole percent of Li in theglass is greater than 40 mol % or greater than 50 mol % or even greaterthan 60 mol %. In various embodiments the glass is substantially devoidof alkali metal ions other than Li.

In various embodiments sulfur (S) is present in the glass to at least 10mol %, and typically significantly higher; for instance, ≥20 mol % of S,or ≥30 mol % of S, or ≥40 mol % of S. In various embodiments theconcentration of sulfur as a constituent element in the glass is between20-60 mol %, or between 30%-50 mol % (e.g., about 25 mol %, about 30 mol%, about 35 mol %, about 40 mol %, about 45 mol %, or about 50 mol %).In various embodiments sulfur is the major elemental constituent of theglass, which is to mean the mol % of sulfur is greater than that of anyother constituent element.

Various Li ion conducting sulfur based glass systems (i.e.,sulfur-containing glasses) are contemplated for use herein. Theseinclude lithium phosphorous sulfide, lithium phosphorous oxysulfide,lithium boron sulfide, lithium boron oxysulfide, lithium boronphosphorous oxysulfide, lithium silicon sulfide, lithium siliconoxysulfide, lithium germanium sulfide, lithium germanium oxysulfide,lithium arsenic sulfide, lithium arsenic oxysulfide, lithium seleniumsulfide, lithium selenium oxysulfide, lithium aluminum sulfide, lithiumaluminum oxysulfide, and combinations thereof.

In various embodiments the sulfur-based glass may include certainadditives and compounds to enhance conductivity or properties generally,such as halide salts (e.g., LiCl, LiBr, LiI), Ga₂S₃, Al₂S₃, nitrogen(e.g., thio-nitrides), as well as phosphate (e.g., lithium phosphate(e.g., Li₃PO₄, LiPO₃), sulfate (e.g., Li₂SO₄), silicate (e.g., Li₄SiO₄)and borate salts (e.g., LiBO₃). In embodiments, constituent elements Al,Sn, F and/or Cl, may be incorporated in the glass. In embodiments,various devitrifying agents may be added to the sulfide glass to enhanceits stability against crystallization. In various embodiments thesulfur-based glass is made in the absence of Ga₂S₃ or Al₂S₃, for examplethe sulfur-based glass devoid of Al or Ga as a constituent element.

In various embodiments the sulfur-based glass is of the type:Li₂S—YS_(n) wherein Y is a glass former constituent element and may beGe, Si, As, B, or P; and wherein n=2, 3/2 or 5/2. For example, invarious embodiments the glass system may be Li₂S—PS_(5/2) orLi₂S—BS_(3/2) or Li₂S—SiS₂.

In various embodiments the sulfur-based glass is of the type:Li₂S—YS_(n)—YO_(n) wherein Y is a glass former constituent element, andmay be Ge, Si, As, B, or P; and wherein n=2, 3/2 or 5/2. For example, invarious embodiments the glass system may be Li₂S—PS_(5/2)-PO_(5/2) orLi₂S—BS_(3/2)-BO_(3/2) or Li₂S—SiS₂—SiO₂.

In various embodiments the sulfur-based glass is of the type:Li₂S—YS_(n); Li₂S—YS_(n)—YO_(n) and combinations thereof; for whichY=Ge, Si, As, B, and P; and n=2, 3/2, 5/2.

In various embodiments the sulfur-based glass is of the type:Li₂S—Y¹S_(n)—Y²O_(m) wherein Y¹ and Y² are different glass formerconstituent elements, and may be Ge, Si, As, B, or P; and wherein n=2,3/2 or 5/2 and m=2, 3/2 or 5/2, as appropriate based on the commonstandard valence of the constituent element. For example, in variousembodiments the glass system may be Li₂S—PS_(5/2)-BO_(3/2) orLi₂S—BS_(3/2)-PO_(5/2) or Li₂S—PS_(5/2)—SiO₂.

In various embodiments, Li₂S may be wholly, or partially, substitutedwith Li₂O.

In various embodiments the glass may be a combination of two or moresuch types; for instance, Li₂S—PS_(5/2)—BS_(3/2) or Li₂S—PS_(5/2)—SiS₂or Li₂S—PS_(5/2)—BS_(3/2)—SiS₂. Specific examples include,Li₂S—PS_(5/2)—PO_(5/2); Li₂S—BS_(3/2)—BO_(3/2); Li₂S—SiS₂—SiO₂;Li₂S—P₂S₅; Li₂S—B₂S₃; Li₂S—SiS₂; Li₂S—P₂S₅—P₂O₅; Li₂S—P₂S₅—P₂O₃;Li₂S—B₂S₃—B₂O₃; Li₂S—P₂S₅—B₂S₃; Li₂S—P₂S₅—B₂S₃—B₂O₃, Li₂S—B₂S₃—P₂O₅;Li₂S—B₂S₅—P₂O₃; Li₂S—SiS₂—P₂O₅; Li₂S—P₂S₅—SiO₂;Li₂S—P₂S₅—P₂O₅—B₂S₃—B₂O₃.

The continuous Li ion conducting inorganic glass may be described ashaving a glass network former that brings about the skeletal lattice anda glass network modifier, such as a lithium compound, that introducesionic bonds and thereby serves as a disrupter of the lattice andprovides mobile lithium ions for conduction. In various embodimentsadditional network formers may be incorporated in the glass. Forinstance, in various embodiments the glass system may have the generalformula:xNET(major former):yNET(minor former):zNET(modifier)

-   -   wherein z=1−(x+y)

NET(major former) is the major glass network former and its molefraction, x, is the largest of all the network formers used to make theglass. Net(minor former) represents one or more minor glass networkformers that is present in the glass with mole fraction, y. In allinstances the mole fraction of the major glass former is larger thanthat of any minor glass former. However, the combined mole fraction ofthe minor glass formers may be greater than that of the major glassformer. NET(modifier) is generally Li₂S or Li₂O or some combinationthereof.

The network former (major or minor) may be a compound of the typeA_(a)R_(b), or a combination of two or more different compounds of thistype. For instance, A may be Silicon, Germanium, Phosphorous, Arsenic,Boron, Sulfur and R may be Oxygen, Sulfur, or Selenium; and the networkmodifier may be of the type N_(m)R_(c), with N being Lithium and R beingOxygen, Sulfur, or Selenium; and a, b, m, and c represent the indicescorresponding to the stoichiometry of the constituents.

In various embodiment the major network former is B₂S₃, P₂S₅ or SiS₂,and the minor network former is one or more of B₂O₃, P₂O₅, P₂O₃, SiO₂,B₂S₃, P₂S₅, SiS₂, Al₂S₃, Li₃PO₄, LiPO₃ Li₂SO₄ LiBO₃. Specific examplesinclude: i) Li₂S as the network modifier, B₂S₃ as the major former, andone or more minor formers selected from the group consisting of B₂O₃,P₂O₅, P₂O₃, SiO₂, P₂S₅, SiS₂, Al₂S₃, Li₃PO₄, LiPO₃ Li₂SO₄ LiBO₃; ii)Li₂S as the network modifier, P₂S₅ as the major former, and one or moreminor formers selected from the group consisting of B₂O₃, P₂O₅, P₂O₃,SiO₂, B₂S₃, SiS₂, Al₂S₃, Li₃PO₄, LiPO₃ Li₂SO₄ LiBO₃; iii) Li₂S as thenetwork modifier, SiS₂ as the major former, and one or more minorformers selected from the group consisting of B₂O₃, P₂O₅, P₂O₃, SiO₂,P₂S₅, B₂S₃, Al₂S₃, Li₃PO₄, LiPO₃ Li₂SO₄ LiBO₃. In various embodiments,the network modifier is Li₂S or Li₂O, or some combination thereof.

Selecting the appropriate sulfide glass composition depends on the endof use of the solid electrolyte sheet, and ultimately on the type andapplication of the battery cell in which it is intended to operate.Among the many potential considerations are form factor, cellconstruction, cost, power requirements, and service life. Accordingly,the glass composition may be adjusted to enhance one or more of i)chemical and electrochemical compatibility of the glass in directcontact with lithium metal and/or a liquid electrolyte; ii) flexibility,shape and size; iii) glass formability (especially as it relates tothermal properties); and iv) Li ion conductivity. Optimizing one or moreof these parameters generally requires a tradeoff.

In various embodiments the sulfide glass system is selected for itschemical and electrochemical compatibility in direct contact withlithium metal.

Chemical compatibility to lithium metal is an attribute that relates tothe kinetic stability of the interface between glass sheet 100 and alithium metal layer, and electrochemical compatibility generallyassesses the ability of that interface to function in a battery cell.Both properties require the formation of a solid electrolyte interphase(SEI) that stops reacting with the glass surface once formed (i.e.,chemical compatibility) and is sufficiently dense and conductive thatits interface resistance is acceptable for its use in a battery cell.

Incorporating certain constituent elements into glass sheet 100 isdesirable for creating an SEI commensurate with both chemical andelectrochemical compatibility. In various embodiments, phosphorous isincorporated as a main constituent element for producing an effectiveSEI, as phosphorous in direct contact with lithium metal reacts to formlithium phosphide (e.g., Li₃P), a compound highly conductive of Li ionsand fully reduced. To form an acceptable SEI, phosphorous may be presentin small amount (e.g., as a secondary constituent of the glass). Addingphosphorous as a secondary constituent element provides an effectivemethod for reducing resistance at the interface, and may be used toeffect compatibility in a glass system, which, as contemplated herein,may not form a stable SEI, such as silicon sulfide glasses, with SiS₂ asthe exclusive network former. Accordingly, in some embodiments, Si maybe intentionally excluded as a constituent element of the sulfide glasssheet 100.

Notably, it has been discovered that phosphorous sulfide glass systemsare not the only glasses chemically and electrochemically compatibilityin direct contact with lithium metal. Surprisingly, boron sulfideglasses, even in the absence of phosphorous, have shown remarkablechemical and electrochemical compatibility against metallic lithium (Limetal). Accordingly, in various embodiments phosphorous may be excludedfrom the glass as a constituent element to mitigate potential issuesassociated with high vapor pressure and chemical reactivity; forexample, the glass substantially devoid of phosphorous. However, insmall amount, adding phosphorous as a secondary constituent element tothe boron sulfide glasses may not impart processing issues, and, asdescribed below, may be added as a method for reducing interfaceresistance in direct contact with Li metal.

In various embodiments adding oxygen and/or silicon provides a methodfor improving thermal properties, especially for enhancing glassformability, including glass stability (e.g., increasing the glassstability factor and/or Hruby parameter) and/or viscosity at theliquidus temperature (T_(liq)). For instance, adding silicon as asecondary constituent to a phosphorous sulfide or boron sulfide glassprovides a method for increasing glass stability and/or viscosity atT_(liq) (i.e., the liquidus viscosity), while retaining compatibility toLi metal. The addition of oxygen as a constituent element may alsoafford benefit in these regards. In various embodiments oxygen may beincorporated as a main or secondary constituent element in lithiumphosphorous sulfide and lithium boron sulfide glass systems as a methodfor increasing the glass stability factor and/or Hruby parameter. Forinstance, xLi₂S-yP₂S₅-zSiS₂, xLi₂S-yB₂S₃-zSiS₂, xLi₂S-yP₂S₅-zSiO₂,xLi₂S-yB₂S₃-zSiO₂, xLi₂S-yB₂S₃-zB₂O₃, xLi₂S-yP₂S₅-zP₂O₅; wherein withx+y+z=1 and x=0.4-0.8, y=0.2-0.6, and z ranging from 0 to 0.2 (e.g.,about 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11,0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2).

Solid electrolyte sheets of silicon sulfide based glasses areparticularly advantageous for use as a separator sheet in battery cellswhich employ a common liquid electrolyte, as described in more detailherein below, or wherein the separator sheet does not contactelectroactive material. For instance, xLi₂S-ySiS₂; xLi₂S-ySiS₂-zSiO₂;xLi₂S-ySiS₂-yB₂S₃; xLi₂S-ySiS₂-yB₂O₃; xLi₂S-y B₂S₃-zSiO₂; wherein withx+y+z=1 and x=0.4-0.8, y=0.2-0.6, and z ranging from 0 to 0.2 (e.g.,about 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11,0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2).

With consideration of the above discussion, it is clear that in limitedamount certain elements can have a beneficial role for enhancingperformance of sheet 100 and/or improving glass stability forprocessing. The addition of phosphorous can reduce interfacialresistance with Li metal and the addition of oxygen can improve glassstability. In a boron sulfide glass, the addition of phosphorous, as asecondary constituent element, can be made via the incorporation of P₂S₅and the addition of oxygen via B₂O₃; yielding the glass system:Li₂S—B₂S₃—P₂S₅—B₂O₃; wherein B₂S₃ is the primary network former, P₂S₅and B₂O₃ are secondary network formers, and Li₂S is the networkmodifier. As such, the oxygen to phosphorous mole ratio can be varied.In another embodiment the phosphorous and oxygen mole ratio may beconstrained by incorporating P₂O₅ as a single ingredient, giving rise tothe glass system Li₂S—B₂S₃—P₂O₅; wherein B₂S₃ is the primary networkformer, P₂O₅ is a secondary former, and Li₂S is the network modifier.

In various embodiments the sulfur-based glass comprises Li₂S and/or Li₂Oas a glass modifier and one or more of a glass former selected from thegroup consisting of P₂S₅, P₂O₅, SiS₂, SiO₂, B₂S₃ and B₂O₃.

Specific examples include, 0.7Li₂S-0.29P₂S₅-0.01P₂O₅;0.7Li₂S-0.28P₂S₅-0.02P₂O₅; 0.7Li₂S-0.27P₂S₅-0.03P₂O₅;0.7Li₂S-0.26P₂S₅-0.04P₂O₅; 0.7Li₂S-0.25P₂S₅-0.05P₂O₅;0.7Li₂S-0.24P₂S₅-0.06P₂O₅; 0.7Li₂S-0.23P₂S₅-0.07P₂O₅;0.7Li₂S-0.22P₂S₅-0.08P₂O₅; 0.7Li₂S-0.21P₂S₅-0.09P₂O₅;0.7Li₂S-0.2P₂S₅-0.1P₂O₅; 0.7Li₂S-0.29B₂S₃-0.01B₂O₃;0.7Li₂S-0.28B₂S₃-0.02B₂O₃; 0.7Li₂S-0.27B₂S₃-0.03B₂O₃;0.7Li₂S-0.26B₂S₃-0.04B₂O₃; 0.7Li₂S-0.25B₂S₃-0.05B₂O₃;0.7Li₂S-0.24B₂S₃-0.06B₂O₃; 0.7Li₂S-0.23B₂S₃-0.07B₂O₃;0.7Li₂S-0.22B₂S₃-0.08B₂O₃; 0.7Li₂S-0.21B₂S₃-0.09B₂O₃;0.7Li₂S-0.20B₂S₃-0.1B₂O₃; 0.7Li₂S-0.29B₂S₃-0.01P₂O₅;0.7Li₂S-0.28B₂S₃-0.02P₂O₅; 0.7Li₂S-0.27B₂S₃-0.03P₂O₅;0.7Li₂S-0.26B₂S₃-0.04P₂O₅; 0.7Li₂S-0.25B₂S₃-0.05P₂O₅;0.7Li₂S-0.24B₂S₃-0.06P₂O₅; 0.7Li₂S-0.23B₂S₃-0.07P₂O₅;0.7Li₂S-0.22B₂S₃-0.08P₂O₅; 0.7Li₂S-0.21B₂S₃-0.09P₂O₅;0.7Li₂S-0.20B₂S₃-0.1P₂O₅; 0.7Li₂S-0.29B₂S₃-0.01SiS₂;0.7Li₂S-0.28B₂S₃-0.02SiS₂; 0.7Li₂S-0.27B₂S₃-0.03 SiS₂;0.7Li₂S-0.26B₂S₃-0.04SiS₂; 0.7Li₂S-0.25B₂S₃-0.05SiS₂;0.7Li₂S-0.24B₂S₃-0.06SiS₂; 0.7Li₂S-0.23B₂S₃-0.07SiS₂;0.7Li₂S-0.22B₂S₃-0.08SiS₂; 0.7Li₂S-0.21B₂S₃-0.09SiS₂;0.7Li₂S-0.20B₂S₃-0.1 SiS₂.

In a particular embodiment, the sulfur-based glass comprises Li₂S and/orLi₂O as a glass modifier, B₂S₃ as the major glass former and SiS₂ as aminor glass former, wherein the amount of SiS₂ is sufficient to yield aglass stability factor greater than 50° C., without decreasing the Liion conductivity below 10⁻⁵ S/cm, and preferably does not decrease below10⁻⁴ S/cm, and more preferably does not decrease below 10⁻³ S/cm.Preferably the glass stability factor is greater than 60° C., and morepreferably greater than 60° C., and even more preferably greater than100° C.

In another particular embodiment, the sulfur-based glass comprises Li₂Sand/or Li₂O as a glass modifier, B₂S₃ as the major glass former and P₂O₅as a minor glass former, wherein the amount of P₂O₅ in the glass issufficient to yield an ASR as measured against Li metal that is lessthan 200 Ω-cm², without decreasing the Li ion conductivity below 10⁻⁵S/cm, and preferably does not decrease below 10⁻⁴ S/cm, and morepreferably does not decrease below 10⁻³ S/cm. Preferably, the ASR isless than 100 Ω-cm², and more preferably less than 50 Ω-cm².

In yet another particular embodiment, the sulfur-based glass comprisesLi₂S and/or Li₂O as a glass modifier, B₂S₃ as the major glass former,and P₂O₅ and SiS₂ as minor glass formers, wherein the amount of SiS₂ andP₂O₅ is sufficient to yield a glass stability factor of no less than 50°C.; an ASR as measured against Li metal that is less than 200 Ω-cm², andwithout decreasing the Li ion conductivity below 10⁻⁵ S/cm, andpreferably does not decrease below 10⁻⁴ S/cm, and more preferably doesnot decrease below 10⁻³ S/cm. Preferably, the ASR is less than 100Ω-cm², and more preferably less than 50 Ω-cm².

In a particular embodiment the vitreous sheet is composed of asulfur-based glass having more than 20 mole % of S as a firstconstituent element; more than 20 mole % of Li as a second constituentelement; more than 20 mole % of a third constituent element selectedfrom the group consisting of B or P; and at least 1 mole % but notgreater than 20 mole % of a fourth constituent element selected from thegroup consisting of O, Si, and a combination of O and Si as the fourthconstituent element(s); wherein the mole % of the fourth constituentelement is sufficient to yield a glass stability factor greater than 50°C., preferably greater than 60° C., more preferably greater than 80° C.,and even more preferably greater than 100° C., without decreasing theconductivity below 10⁻⁵ S/cm, and preferably without decreasing theconductivity below 10⁻⁴ S/cm, and more preferably without decreasing theconductivity below 10⁻³ S/cm.

In another particular embodiment, the vitreous sheet is composed of asulfur-based glass having more than 20 mole % of S as a firstconstituent element; more than 20 mole % of Li as a second constituentelement; more than 20 mole % of a third constituent element selectedfrom the group consisting of B or P; and at least 1 mole % but notgreater than 20 mole % of a fourth constituent element selected from thegroup consisting of O, Si, and a combination of O and Si as the fourthconstituent element(s); wherein the mole % of the fourth constituentelement(s) is sufficient to effect a viscosity at T_(liq) that isgreater than 200 poise, preferably greater than 500 poise, morepreferably greater than 1,000 poise, and even more preferably greaterthan 3000 poise, without decreasing the conductivity below 10⁻⁵ S/cm,preferably without decreasing the conductivity below 10⁻⁴ S/cm, and morepreferably without decreasing the conductivity below 10⁻³ S/cm.

In yet another particular embodiment, the vitreous sheet is composed ofa sulfur-based glass having The standalone Li ion conductive solidelectrolyte separator of claim 2, wherein the sulfur-based glass furthercomprises: more than 20 mole % of S as a first constituent element; morethan 20 mole % of Li as a second constituent element; more than 20 mole% of a third constituent element selected from the group consisting ofSi or B; and at least 1 mole % but not greater than 20 mole % of P as afourth constituent element; wherein the mole % of P is sufficient toeffect an ASR for the vitreous sheet, as measured between opposingprincipal sides in direct contact with Li metal, that is less than 200Ω-cm², preferably less than 100 Ω-cm², and more preferably less than 50Ω-cm², without decreasing the conductivity of the sheet below 10⁻⁵ S/cm,preferably without decreasing the conductivity below 10⁻⁴ S/cm, and morepreferably without decreasing the conductivity below 10⁻³ S/cm.

The Li ion conductive glass phases having conductivity ≥10⁻⁵ S/cm,preferably ≥10⁻⁴ S/cm and more preferably ≥10⁻³ S/cm are embodied hereinabove by sulfide glasses, however the disclosure contemplatesalternatives, including those which are based on selenium and/or oxygen,and may be devoid of sulfur. Accordingly, it is contemplated that theinstant disclosure may be embodied by Li ion conducting oxide, phosphateand silicate glasses. Other amorphous phases are also contemplated, suchas glassy lithium halides (e.g., Li_(3-2x)M_(x)Halo; wherein M istypically a cation of valence ≥2, such as Mg, Ca or Ba, and Hal is ahalide such as Cl, I or a mixture thereof).

A battery serviceable solid electrolyte sheet devoid of continuousinterconnected pathways into which lithium metal dendrites could growand ultimately short circuit through the sheet is described. The sheetis generally embodied by high Li ion conductivity sulfide-based glass(i.e., sulfur-containing glass).

While this disclosure is not limited by any particular theory ofoperation, it is believed that the ability of the instant solidelectrolyte sheet to resist and preferably prevent dendritic throughpenetration in a lithium battery cell is based on it having a bulkmicrostructure that is absent of continuous chain-like voids extendingbetween the first and second principal side surfaces, and, inparticular, continuous void-like discontinuities in the form ofcrystalline grain boundaries and/or particle-to-particle boundaries, asdefined above. Preferably, the surface of the solid electrolyte sheet isliquid-like, by which it is meant a smooth amorphous surface, asresulting from the action of surface tension on a quiescent liquid.

To create such a bulk microstructure and liquid-like surface, theinstant solid electrolyte sheet is composed in whole or in part of acontinuous vitreous glass phase (i.e., a vitreous material expanse)configured to intersect potential dendritic pathways while providingconduction for Li ions.

With reference to FIGS. 4A-H there is illustrated cross sectional viewsof Li ion conductive solid electrolyte sheets 400A-H in accordance withvarious embodiments of the disclosure. While each of the sheets has asomewhat distinct microstructure, or microstructural feature(s), whenconsidered in totality of their respective bulk and surfacemicrostructures, they all result in the common aspect of being resistantto facile through penetration of lithium metal dendrites. Accordingly,sheet 400A-H is devoid of chain-like voids in the form of discreteand/or pressed powder inter-particle boundaries, especially amorphouspowder inter-particle boundaries, and interconnected continuouscrystalline grain boundaries extending across the thickness of thesheet.

With reference to FIGS. 4A-E, solid electrolyte sheet 100 is embodied asa vitreous monolith of a Li ion conducting sulfide based glass 400A-E.

Vitreous monoliths 400A-E are each composed of a vitreous sulfide glassphase 401 that is continuous throughout its respective sheet and hasroom temperature intrinsic Li ion conductivity ≥10⁻⁵ S/cm, preferably≥10⁻⁴ S/cm, and more preferably ≥10⁻³ S/cm. The vitreous sulfide glassphase constitutes a majority volume fraction of the monolithic sheet,and thus is considered the primary material phase. In variousembodiments, the vitreous sulfide glass phase is not only the primarymaterial phase of the sheet, and pervasive throughout, it alsorepresents a significant volume fraction of the monolith, as well as amajority of the area fraction of its first and second principal sidesurfaces.

When the volume fraction of the primary sulfide glass phase is less than100%, the remaining solid volume is generally accounted for by secondaryphase(s), which may be crystalline 403 or amorphous 405. In suchembodiments, the continuous Li ion conducting primary glass phase 401effectively serves as a glass matrix with the secondary phases 403/405embedded and typically isolated therein. In various embodiments, thecontinuous Li ion conducting sulfur-based glass phase 401 is not onlythe primary material phase of the sheet, as defined above, it alsoconstitutes a majority area fraction of the first and/or secondprincipal side surfaces (e.g., at least 50%, at least 60%, at least 70%,at least 80%, at least 90%, or at least 95%, and preferably 100% of thefirst and/or second principal side surface(s) is defined by thecontinuous Li ion conducting glass phase).

Preferably, the first and second principal side surfaces of the vitreousmonolithic solid electrolyte sheets are essentially free of crystallinephases, and more preferably the surfaces are essentially free ofsecondary phases, including both crystalline phases and secondaryamorphous phases. Preferably, the vitreous monolithic sheet of Liion-conducting glass is amorphous as determined by X-ray diffraction andpreferably essentially free of crystalline phases, and more preferablycompletely devoid of any detectable crystalline phases or inclusions.Preferably the vitreous monolithic sheet of Li ion conducting glass ishomogeneous and thus devoid of secondary phases that derive from theglass composition itself. During processing the solid electrolyte glassmay come into contact with external contaminates that can lead toimpurity phases, the origin of which is not solely the glass compositionitself, but rather derived from contact with a foreign material duringprocessing or from an impurity present in a precursor material. Any suchcontamination should be minimized, if not fully eliminated. Preferably,the vitreous monolith is essentially free of any such impurity or pointtype defects, such as stones of refractory material or crystallinerefractory phases (e.g., α-alumina, zirconia, and α-quartz) and gaseousinclusions (i.e., bubbles), which may form as a result of impuritiesreacting with the glass composition, including impurities present in theenvironment about which the sheet is processed.

The vitreous monolithic sheets of this disclosure are further advantagedby the quality of their bulk and surface, and, in particular, a lack offlaws normally associated with sulfide glass particle compaction,including an undue density of internal pores and irregularly shapedsurface voids, both of which are commonplace for die pressed andhot-pressed sulfide glass powder compacts. Preferably, the vitreoussolid electrolyte sheets of this disclosure have a very lowconcentration of internal pores and surface voids; for instance, aconcentration of internal micropores less than 100 micropores/1000 um³,and preferably less than 50 micropores/1000 um³, and more preferablyless than 10 micropores/1000 um³; ii) a concentration of internalnanopores less than 100 nanopores/1000 um³, more preferably less than 50nanopores/1000 um³, and even more preferably less than 10 nanopores/1000um³; iii) a concentration of surface microvoids less than 10micropores/cm² and preferably less than 10 micropores/cm²; and iv) aconcentration of surface nanovoids less than 50 nanovoids/cm²; morepreferably less than 25 surface nanovoids/cm², and even more preferablyless than 10 surface nanovoids/cm².

In preferred embodiments, the vitreous monolithic solid electrolytesheet is essentially free of internal micropores and surface microvoids(i.e., none are observable), and even more preferably the vitreous solidelectrolyte sheet is substantially free of internal nanopores (≤2nanopores/1000 um³) and substantially free of surface nanovoids (≤2nanovoids/cm²), and yet even more preferably essentially free ofinternal nanopores and surface nanovoids. Since surface voids andinternal pores may be irregularly shaped; the equivalent diameter of apore is taken to be the maximum diameter of a circle inscribed about thepore. By use of the term “microvoid” or “micropore” it is meant avoid/pore having a minimum diameter ≥1 um and up to about 100 μm(microvoid), and by “nanovoid” or “nanopore” it is meant a void/porehaving a minimum diameter ≥10 nm but <1 um.

With reference to FIG. 4A, substantially amorphous vitreous monolith400A essentially consists of the primary sulfide glass phase 401A, whichconstitutes more than 95%, and preferably 100% of the total sheetvolume, with the remaining volume fraction (i.e., less than 5%), if any,accounted for by incidental secondary phases embedded within the primaryglass phase. Preferably substantially amorphous sheet 400A isessentially free of crystalline phases and completely amorphous asdetermined by X-ray diffraction, and more preferably it is completelydevoid of crystalline phases (i.e., none detectable). In a preferredembodiment, sheet 400A is a homogeneous vitreous sulfide-based glasssheet, essentially free of secondary phases, including crystallinephases and secondary amorphous phases, and preferably entirely devoid ofsecondary phases (i.e., none are detectable). Preferably the firstprincipal side surface is liquid-like, with an exceptionally smoothtopography having an average surface roughness R_(a)<0.1 um, preferably<0.05 um, more preferably R_(a)<0.01 um, and even more preferablyR_(a)<0.005 um, and yet even more preferably R_(a)<0.001 um.

With reference to the cross sectional bulk microstructure depicted inFIG. 4B, in other embodiments, the vitreous monolithic sulfide-basedsolid electrolyte sheet 400B is substantially amorphous, but contains atleast a discernable amount of crystalline phases/regions 403B, typicallyisolated and appearing as inclusions embedded in the continuous vitreousglass matrix phase 401B, with the proviso that the crystallinephases/regions do not, in combination, create a continuous grainboundary pathway across the thickness of the sheet. In variousembodiments, substantially amorphous sheet 400B contains a volumefraction of crystalline phases that is between 5-20 vol %. Inalternative embodiments, the fraction of crystalline phases is greaterthan 20 vol % but typically less than 70 vol %. The acceptable volumefraction depends on several factors, including the desired flexibilityof the sheet as well as the spatial distribution and Li ion conductivityof the crystalline phases themselves. In various embodiments, thecrystalline phases are highly conductive of Li ions (preferably,σ^(□□)>10⁻⁴ S/cm) and may have a volume fraction greater than 20% (e.g.,in the range of 50-70 vol %), provided that the Li ion conductiveprimary glass matrix remains continuous and extensive throughout thesheet, and that the crystalline phases are sufficiently spaced apart tonot percolate in contiguity across the sheet (along the thicknessdirection). In various embodiments the volume fraction of crystallinephases embedded in the continuous vitreous sulfur-based glass matrixphase is in the range of 5-10 vol %; 10-20 vol %; 20-30 vol %; 40-50 vol%; 50-60 vol %; and 60-70 vol %.

As illustrated in FIG. 4C, with respect to monolith 400C, the first andsecond principal side surfaces are essentially free of crystallinephases, despite the fact that the monolith itself contains some amountin its bulk. And more preferably the surface(s) are entirely devoid ofdetectable crystalline phases. For instance, it is contemplated that themonolith may be surface treated with heat to dissolve the crystallinephases.

With reference to FIGS. 4D-E, there are illustrated cross sectionaldepictions of a substantially amorphous vitreous monolithic sulfur basedsolid electrolyte glass sheet that is preferably essentially free ofcrystalline phases but contains some amount of secondary amorphousphases 407D embedded in the continuous primary sulfur-based Li ionconducting glass phase 401D. Preferably, the secondary phase(s) isconductive of Li ions (σ^(□□)>10⁻⁷ S/cm), and more preferably highlyconductive (σ^(□□)>10⁻⁵ S/cm). In accordance with this embodiment, thevolume fraction of the secondary amorphous/glass phase(s) may besignificant, and greater than 5 vol %. In various embodiments, thevolume fraction of secondary phases is in the range of 5-10 vol %; 10-20vol %; 20-30 vol %; 40-50 vol %; 50-60 vol %; 60-70 vol %; 70-80 vol %,provided that the primary sulfur based glass matrix phase retains itscontinuity throughout the sheet, and that the interfaces between thesecondary amorphous phases and the primary phase do not create acontiguous phase boundary continuous between the first and secondprincipal side surfaces. As illustrated in FIG. 4E, preferably themajority of the secondary phases are present in the bulk of the sheet,and the first and second principal side surfaces are essentially free ofsecondary phases (i.e., an area fraction less than 2%), and morepreferably there are no detectable secondary phases on either principalside surface.

In an alternative embodiment, solid electrolyte sheet 100 may beembodied by two or more substantially amorphous and continuous vitreousglass matrices (layer-like), each a continuous layer-like matrixcomposed of a different Li ion conducting sulfide-based glass havingroom temperature intrinsic Li ion conductivity ≥10⁻⁵ S/cm. Asillustrated in the cross sectional depiction shown in FIG. 4F, solidelectrolyte sheet 400F is composed of two vitreous matrix layers: afirst substantially amorphous vitreous matrix 401F and a secondsubstantially amorphous vitreous matrix 402F, each defining the firstand second principal side surfaces of the sheet respectively. In variousembodiments, first vitreous glass matrix 401F is chemically compatiblein direct contact with lithium metal and second vitreous glass matrix402F is not chemically compatible with lithium metal. In otherembodiments, both first and second vitreous matrix layers are chemicallycompatible with lithium metal. While the illustrated embodiment iscomposed of two vitreous matrix layers, the disclosure contemplatesmultiple vitreous sulfide glass matrix layers (e.g., three or more). Invarious embodiments one or both vitreous matrix layers 401F/402F areessentially free of crystalline phases, and in preferred embodimentseach vitreous matrix layer is a homogeneous vitreous glass layeressentially free of secondary phases (crystalline or amorphous).Preferably, each vitreous matrix layer is entirely devoid of detectablesecondary phases. For example, solid electrolyte sheet 400F may befabricated using a fusion draw process wherein two different glassstreams are fusion bonded to each during the drawing step, as describedin more detail herein below.

With reference to FIGS. 4G-H, there is illustrated cross sectionaldepictions of freestanding sulfide based solid electrolyte sheets inaccordance with other alternative embodiments of this disclosure. Inaccordance with these embodiments, the bulk microstructure of the solidelectrolyte sheet 400G/400H is not fully vitreous, but rather the sheethas a composite microstructure composed of a region 410 which forms theinterior and is made by compaction of Li ion conducting sulfide glassparticles, sulfide glass-ceramic particles, sulfide polycrystallineparticles, or some combination thereof (typically sulfide glassparticles), and a substantially amorphous vitreous stratum 420 of Li ionconducting sulfide glass, which defines at least the first principalside surface of sheet 400G/400H. With reference to FIG. 4G, solidelectrolyte sheet 400G has first and second vitreous strata 420 i/420 ii(e.g., composed of first and second glass matrix phases in the form of astratum) defining the first and second principal side surfacesrespectively. With reference to FIG. 411 , solid electrolyte sheet 40011has a single vitreous stratum 420 defining the first principal sidesurface. The vitreous stratum may be formed by a rapid surface meltingoperation (e.g., using a laser or hot gas), followed by a coolingquench. Preferably the vitreous stratum is essentially free ofcrystalline phases, and even more preferably the stratum, homogeneous,is essentially free of secondary phases. Typically the sulfide glasscomposition of the stratum and that of the particle compact region issubstantially the same.

In addition to enabling flexibility, and substantial dendriteimpenetrability, physical aspects of the surface can also be importantfor effecting and maintaining a tight interface with a lithium metallayer, and this is important for achieving uniform plating and stripingof lithium metal, high lithium metal cycling efficiency (>99%), andultimately a long cycle life lithium battery cell. Accordingly, invarious embodiments, the principal side of sheet 100 in contact withlithium metal (i.e., first principal side 101A) should have aliquid-like surface that is also flat. Deviations from flatness canresult in impedance variability as waviness can cause local positionalvariance of the ionic sheet resistance, leading to uneven Li metalplating and striping reactions resulting from non-uniform currentdensity across the solid electrolyte sheet. As opposed to surfaceroughness, surface waviness W_(a) is defined by a larger sampling length(typically >0.5 cm), and thus is an important factor for achieving adesirably uniform and homogeneous lithium plating morphology. In variousembodiments, the waviness of first principal side surface 101A is lowenough to maintain a gap free interface with the lithium metal layerupon repeated plating and striping of lithium metal; and, in particular,the level of waviness is sufficiently low to maintain a gap freeinterface after 50 charge cycles at an area ampere-hour chargingcapacity of >1 mAh/cm². Preferably the waviness of the sheet is lessthan 5 μm, and even more preferably less than 1 μm, and yet even morepreferably less than 0.5 μm. For instance, in various embodiments, theacceptable level of waviness will depend on the thickness of the sheetitself. And thus, for a sheet having thickness in the range of about Sumto 10 μm, W_(a) is preferably less 1 um; for a sheet having a thicknessin the range of about 10 μm to 20 μm, W_(a) is preferably less than 1um, and even more preferably less than 0.5 μm; for a sheet having athickness in the range of about 20 μm to 50 μm, W_(a) is preferably lessthan 5 μm, and even more preferably less than 2 um, and yet even morepreferably less than 1 μm; for a sheet having a thickness >50 μm (e.g.,about 100 μm, 150 μm or 200 μm), W_(a) is preferably less than 10 μm,and even more preferably less than Sum, and yet even more preferablyless than 2 μm.

The ability to achieve long cycle life in a lithium metal battery cellof high energy density (preferably >250 Wh/l, and more preferably >500Wh/l) depends not only on preventing dendritic shorting, which iscertainly a requisite feature, but also requires high efficiency (>99%)and cycling at significant electrode area ampere-hour capacities(typically >1 mAh/cm²). The chemical and physical interface between thesheet and the lithium metal layer are important considerations forcycling efficiency. As described in more detail below, the sheet surfacecomposition is a key factor in determining the chemical interface,whereas the structure of the interface (i.e., the physical interface),is a function of both the surface composition and the surfacetopography, and, in particular, surface roughness is an importantconsideration, especially as it pertains to the morphology of lithiummetal plated during charging of a battery cell in which sheet 100 isutilized. A sheet surface (e.g., principal side surface 101A) that istoo rough can lead to a porous plating morphology, and thereby a porousinterface of high surface area, and ultimately low cycling efficiency. Asmooth surface is therefore desirable for achieving lithium metalcycling efficiency >99.0%, and preferably >99.2%, and morepreferably >99.5%, and even more preferably >99.8%. Accordingly, invarious embodiments the major area portion of the first principal sidesurface of the instant sheet has an average surface roughness R_(a) thatis sufficient to yield a dense interface between the lithium metal layerand the sheet, and in particular the lithium metal layer-like regionimmediately adjacent to the sheet is preferably >90% dense after 50cycles under a charge corresponding to at least 1 mAh/cm², and morepreferably >90% dense after 100 cycles under said charging condition,and more preferably >90% dense after 200 cycles. Accordingly, in variousembodiments the average surface roughness of the major area portion ofthe first principal side surface is R_(a)<0.2 μm, preferably R_(a)<0.1μm, or R_(a)≤0.05 μm, and even more preferably R_(a)≤0.05 μm, and yeteven more preferably R_(a)≤0.01 μm. In other embodiments, as detailedherein below, having a surface topography with a controlled uniformsurface roughness can be of benefit for bonding material layers, such asa lithium metal layer to the solid electrolyte during fabrication. Forinstance, in various embodiments, smooth first principal side surface101A may be intentially roughened, in a controlled manner, to effect auniform surface roughness >0.2 μm (e.g., between 0.5 to 1 μm).

Preferably the afore described smoothness (R_(a)) and flatness (W_(a))values are obtained in the virgin state, and by this expedientcircumvents the costly and potentially prohibitive steps of grinding andpolishing, and furthermore enables production of solid electrolytesheets with pristine first and second principal side surfaces, which areuntouched by an abrasive foreign solid surface, and therefore preferablyof very high cleanliness values.

In addition to roughness and flatness, surface cleanliness is also aconsideration for achieving a tight consistent interface between sheet100 and a lithium metal layer or plated lithium metal, and thus inembodiments the glass inspection (GI) value of first principal sidesurface 101A is preferably less 1000 pcs/m² and more preferably lessthan 500 pcs/m², wherein the GI value is defined as the number ofimpurity particles having a major diameter of 1 nm or more and existingin a region of 1 m².

Preferably, sheet 100 is of optical quality, by which it is meant thatthe sheet has a surface roughness R_(a)≤0.02 μm and is essentially freeof: i) crystalline phases ii) surface microvoids; and iii) internalnanopores. Preferably, the optical quality of the vitreous sheet isobtained in its virgin state as a solid.

Mechanical failure of any glass (e.g., window glass) will occur when thestress and defect size reach a critical combination. The reliability istherefore statistical, but nonetheless related to the largest sizedflaws on the surface. In contrast, small shallow flaws are perceived asless important, since the underlying mechanical strength of the sheet islargely unaffected by their existence. When shallow flaws are small innumber density, or even singular, their very existence is generallyconsidered insignificant from a practical perspective.

At practical current densities however, as described further herein, ashallow flaw at an otherwise liquid-like surface can be prohibitive forrealizing a dendrite resistant solid electrolyte glass sheet, if theflaw depth is beyond a threshold size for dendrite initiation. Withreference to FIG. 4 i , in a lithium metal battery cell, wherein firstprincipal side surface 101A of vitreous solid electrolyte sheet 100 isin contact with a solid Li metal layer 415, a flaw extending beyond athreshold depth can create a highly localized hot spot for currentfocusing, which can lead to very high local current densities anddendritic penetration of Li metal into the sheet during cell charging,even for electrolytes with elastic moduli well above 20 GPa.

The threshold flaw depth is determined by several factors, including thedetailed flaw geometry, the effective fracture toughness of theelectrolyte, K_(kc) ^(eff) which is typically less than the fracturetoughness determined from a mechanical fracture test, K_(lc), the sheetthickness (t), and the local current density, I_(local), which in turnis proportional to the nominal lithium anode current density,I_(nominal). The general functional relationship for the nominal lithiumanode current density, I_(thr), may be expressed asI _(thr) =f(K _(lc) ^(eff) ,t/(Γ,ν,I _(local)))where

-   -   K_(lc) ^(eff) is the effective fracture toughness at the flaw        tip where flaw extension most readily occurs    -   Γ is the deepest flaw extension into the solid electrolyte    -   t is the sheet thickness    -   ν is the viscosity or the equivalent flow stress (both        temperature dependent) of the solid lithium, and    -   I_(local) is the solid electrolyte/lithium metal anode interface        current density in the immediate vicinity of the surface flaw.        Typically I_(local)>I_(nominal).

To mitigate dendrite propagation through a solid electrolyte sheethaving a liquid-like surface in direct contact with a solid lithiummetal layer, the deepest flaw extension F into the sheet should be lessthan 1% of the sheet thickness, and preferably less than 0.1%, andcertainly no more than 5 μm. For example, the deepest flaw extension ina 100 μm thick sheet should be less than 1 μm, and preferably less than0.1 μm; and for a 50 μm thick sheet it should be less than 0.5 μm, andpreferably less than 0.05 μm.

Moreover, threshold current densities associated with dendriteinitiation can be determined experimentally, or can be estimated fromanalytical approximations to the associated fracturemechanics-electrochemical problem. Typical experiments onpolycrystalline solid electrolytes in direct contact with solid lithiummetal anodes have typically shown threshold charging current densitiesfor dendrite initiation below 0.5 mA/cm′. In contrast, vitreous sulfidesolid electrolytes with smooth interfaces, such as prepared by themethods contemplated herein, have surprisingly sustained currentdensities in excess of 2 mA/cm² without dendrite penetration, whencycling 2 mAh/cm² of lithium metal for over 50 cycles. Subject to theseprinciples, the inventors are now able to characterize the surfacequality of the sheet based on experimentally determined values forI_(thr), by cycling a solid lithium metal layer in direct contact withfirst principal side surface 101A of solid electrolyte sheet 100 at 1mAh/cm² for at least 50 charge cycles without propagating a dendriteacross the sheet. In various embodiments the solid electrolyte sheet ischaracterized as having a surface quality commensurate with an I_(thr)no less than 1 mA/cm², preferably no less than 2 mA/cm², more preferablyI_(thr) is no less than 3 mA/cm², even more preferably I_(thr) is noless than 4 mA/cm², and yet even more preferably I_(thr) is no less than5 mA/cm².

Considering the sensitivity of dendrite initiation to the presence ofshallow flaws, in order for the vitreous solid electrolyte sheet toretain its I_(thr) value during handling and downstream processing ofcell components and cells, special care should be given to minimizecontact damage.

With reference to FIG. 5A, in various embodiments, sheet 100 may be usedas a solid electrolyte separator in a lithium battery cell 500A disposedbetween positive electrode 520A and negative electrode 510A. Typicallybattery cell 500A is a secondary cell (i.e., rechargeable).

In various embodiments battery cell 500A may be fully solid state orinclude a liquid/gel phase electrolyte. In various embodiments theliquid phase electrolyte contacts the electroactive material of thepositive electrode but does not contact the electroactive material ofthe negative electrode, and in such embodiments the cell is referred toherein as a hybrid or a hybrid cell. In some embodiments the liquidelectrolyte is continuous and contacts both the positive and negativeelectrodes, and such cells are referred to herein as having a commonelectrolyte (i.e., the electrolyte is common to both electrodes). Inother embodiments the cell has two discrete liquid phase electrolytesthat do not contact each other: i) a first liquid phase electrolyte thatcontacts the electroactive material of the positive electrode but doesnot contact the negative electroactive material, and may be referred toherein as catholyte; and ii) a second liquid phase electrolyte thatcontacts the electroactive material of the negative electrode but doesnot contact the positive electroactive material, and may be referred toherein as anolyte.

In various embodiments the negative electroactive material is lithiummetal. In various embodiments the positive electroactive material is alithium ion intercalating material. In particular embodiments thenegative electroactive material is lithium metal and the positiveelectroactive material is a Li intercalation compound. In variousembodiments the battery cells of the present disclosure are of a Li iontype, and make use Li ion intercalating material as the electroactivematerial in the negative and positive electrode respectively. Forinstance, Li ion intercalating carbon(s) and/or silicon for the negativeelectrode and Li ion intercalating transition metal oxides,sulfates/sulfides, phosphates/phosphides for the positive electrode.

Continuing with reference to FIG. 5A, in a particular embodiment cell500A is rechargeable, and negative electrode 510A comprises a lithiummetal layer (e.g., a lithium metal foil and/or an evaporated lithiummetal layer) as the negative electroactive layer in direct contact withthe first principal side surface of solid electrolyte sheet 100 (e.g., avitreous sulfide glass sheet of thickness no greater than 100 μm). Invarious embodiments, the rechargeable lithium metal battery cell has: i)a rated ampere-hour capacity in the range of 0.5 mAh-10 Ah (e.g., about1 Ah, about 2 Ah, about 3 Ah, about 4 Ah, or about 5 Ah); ii) a ratedlithium metal electrode area capacity of about 1.0 mAh/cm², or about 2mAh/cm², or about 3 mAh/cm²; and is cycled for more than 50 cycleswithout propagating a dendrite at a discharge/charge current thatcorresponds to C-rate cycling. Preferably, the cell cycles under thesame conditions for greater than 100 cycles without propagating adendrite, and even more preferably for greater than 500 cycles. By useof the term rated area capacity it is meant the capacity at which thecell is cycled.

With reference to FIG. 5B, in various embodiments, sheet 100 serves as aseparator layer (or substrate-sheet) in a lithium metal electrodeassembly 500B; the assembly composed of solid electrolyte sheet 100serving as a substrate for a lithium metal electroactive layer 510Bdisposed adjacent first principal side 101A. In various embodimentslithium metal electroactive layer 510B of assembly 500B is a foil ofextruded lithium metal adhered directly to surface 101A or via atransient tie-layer, such as a metal coating that reacts (e.g., alloys)with the extruded lithium film on contact to form an electrochemicallyoperable interface. In various embodiments, lithium metal layer 510B maybe a coating deposited by physical vapor deposition directly ontosurface 101A (e.g., evaporation or sputtering) or via a tie-layercoating as described above. As discussed in more detail below, whenapplying an extruded lithium metal layer, the lithium metal surface ispreferably fresh; for example, freshly extruded or freshly treated toexpose a fresh Li surface.

With reference to FIG. 5C, in various embodiments lithium electrodeassembly 500B is incorporated in hybrid battery cell 500C. The cellincludes positive electrode 520C, lithium electrode assembly 500B,serving as a fully solid-state negative electrode, and optionalliquid/gel electrolyte layer 530C between sheet 100 and positiveelectrode 520A. In embodiments, battery cell 500C makes use of a liquidelectrolyte in contact with the positive electrode (e.g., a catholyte).Optional electrolyte layer 530C may be composed, in whole or in part, ofthe liquid phase catholyte. In various embodiments electrolyte layer530C comprises a porous separator layer or gel layer impregnated withthe liquid phase catholyte. In embodiments, wherein a liquid phasecatholyte is used, it should be selected to ensure that it is chemicallycompatible in direct contact with the second principal side surface 101Bof solid electrolyte sheet 100, and solid electrolyte sheet 100 shouldalso be chemically compatible with and substantially impervious to theliquid catholyte. To prevent contact between the liquid phaseelectrolyte (i.e., catholyte) and lithium metal layer 510B, in variousembodiments the lithium electrode assembly includes a backplanecomponent seal and an edge seal that isolates the lithium metal layer510B from the catholyte. For instance, the lithium layer effectivelyhoused in a liquid impermeable compartment wherein solid electrolytesheet 100 provides at least one major wall portion. In anotherembodiment of a hybrid cell, it is contemplated that the electrodeassembly may be a positive electrode assembly, wherein the electroactivematerial of the positive electrode (e.g., a Li ion intercalationmaterial) and a liquid phase catholyte are combined and encapsulatedinside a liquid impermeable compartment composed of first and secondsolid electrolyte sheets edge sealed to each other.

Methods for making Li ion conducting solid electrolyte sheet 100 inaccordance with the instant disclosure are provided, and, in variousembodiments, for making a dense substantially amorphous vitreous sheetof sulfide based Li ion conducting glass.

In various embodiments, the method involves solidifying an inorganicfluid sheet of unbroken continuity having a composition corresponding tothat of a Li ion conducting glass with a room temperature intrinsic Liion conductivity ≥10⁻⁵ S/cm, preferably ≥10⁻⁴ S/cm, and more preferably≥10⁻³ S/cm (e.g., a sulfide-based glass). In particular embodiments, thefluid sheet of sulfide glass is caused to flow along its lengthwisedimension as a continuous fluid stream having substantially parallellengthwise edges, and then solidified to form the vitreous solidelectrolyte sheet, mother-sheet or web.

Preferably the fluid stream is, itself, thin and of uniform thickness,as described above. In various embodiments the sulfide glass is airsensitive, and the processes used in making the instant vitreous sheetis performed in an atmosphere substantially devoid of moisture andoxygen (e.g., dry air or dry nitrogen or dry argon).

In various embodiments, the solidified fluid stream is a long solidelectrolyte sheet of vitreous sulfide glass with area aspect ratio >2,and typically >5, and more typically >10. In various embodiments, themethods are suitable for making a very long vitreous Li ion conductingglass sheet; for instance, >10 cm, >50 cm, and in embodiments >100 cmlong and typically at least 1 cm wide, and more typically between 2-10cm wide (e.g., about 2 cm, 3 cm, 4 cm, or about 5 cm wide).

In embodiments the fluid stream, as it flows, is unconstrained along itslengthwise edges and does not expand in a widthwise direction. Invarious embodiments the thin fluid stream of uniform thickness issubstantially untouched by a foreign solid surface upon solidification.In various embodiments, the fluid stream is a vitreous sulfide basedglass, preferably essentially free of crystalline phases, and morepreferably homogeneous (i.e., essentially free of secondary phases,crystalline or amorphous).

To facilitate flow, the fluid stream may have a viscosity low enough toallow it to flow under its own weight. In various embodiments, the fluidstream is caused to flow under the force of gravity while retaining itssheet-like shape, or by pulling/drawing (e.g., via motorized rollers),and in an alternative embodiment, the vitreous solid electrolyte sheetis made by a novel capillary draw method wherein the fluid stream isdriven to flow by capillary forces.

In some embodiments the fluid stream is formed directly from a liquidmelt of Li ion conducting sulfide glass composition, and the liquidstream of molten glass, so formed, is cooled from T_(liq), or aboutT_(m) (e.g., a temperature slightly above the liquidus temperature), toa temperature below the glass transition temperature (T_(g)). Thecooling process may be natural or facilitated to cause solidificationwithin a time frame sufficient to yield the instant freestanding sulfidebased solid electrolyte sheet substantially amorphous and preferablyessentially free of crystalline phases. Preferably, the sulfide basedsolid electrolyte glass composition is selected such that it can berepeatedly heated and cooled between the solid glass phase and theliquid melt phase without crystallizing, phase segregating, orundergoing any other adverse thermal event.

In other embodiments sheet 100 is formed by: i) heating a section of aLi ion conducting sulfide glass preform above its T_(g), ii) pulling onthe preform; and iii) cooling the fluid stream so formed to atemperature below T_(g). The heated section of the preform reaches atemperature above T_(g) but below T_(m), and preferably below T_(x)(i.e., the crystallization temperature upon heating). In variousembodiments, the Li ion conducting sulfide glass preform is itself avitreous, and made by melting and quenching the glass to a desired shapeand size, or by melting and quenching the glass to a large construct,and then sizing down the construct (e.g., by cutting, grinding and/ordrawing) to the shape and dimension desired of the preform.

Similar to a mother-sheet, the fluid stream from which it is derived mayalso be characterized as having a high quality center portion (i.e.,major area portion) and peripheral edge portions, which, when comparedto the center portion, may be of a different thickness, lower surfacequality, and/or having poor thickness uniformity. Preferably, the highquality center portion of the fluid glass stream defines >30% of thetotal area (or total volume) of the fluid stream, and morepreferably >50%, >70%, and even more preferably >90%. In variousembodiments the high quality center portion of the fluid stream is thin(≤500 μm) with a uniform thickness (e.g., about 20 μm, about 30 μm,about 40 μm, about 50 μm, about 60 μm about 70 μm, about 80 μm, about 90μm or about 100 μm). In various embodiments the length and width of thehigh quality center portion of the thin fluid stream is greater than 10cm long (e.g., greater than 50 cm or greater than 100 cm) and greaterthan 1 cm wide; for instance between 2-10 cm wide (e.g., about 2 cm,about 3 cm about 4 cm, about 5 cm, about 6 cm, about 7 cm, about 8 cm,about 9 cm or about 10 cm). In some embodiments the fluid stream is ofsufficient surface quality and thickness uniformity across its entirelength and width, that whence solidified, the solid electrolyte sheet orweb formed there from does not require removal of edge portions, exceptoptionally for the purpose of sizing. In various embodiments, the majoropposing surfaces of the high quality center portion of the fluid streamare pristine, and thus untouched by a foreign solid surface immediatelyprior to solidification. For instance, the fluid stream is caused toflow and traversed by edge rollers and/or edge guide rolls in directcontact with the solidified peripheral edge portions but not the centerportion from which the separator sheets are ultimately cut-to-size.

In various embodiments, drawing techniques such as melt draw and preformdraw are used to make the fluid stream of unbroken continuity, andultimately the solid electrolyte sheet. Draw processing yields theadvantage of naturally developed shapes and surfaces, and thus thegeometric shape (e.g., substantially parallel lengthwise edges),thickness and/or surface topography of the solid electrolyte sheet maymanifest directly from the as-solidified fluid stream (i.e., from thesheet in its virgin state as a solid).

In various embodiments, the sulfide glass compositions are selectedbased on the separation between T_(x) and T_(g) (i.e., the glassstability factor). Preferably the glass composition has a glassstability factor ≥100° C. However, sulfide-based glasses in accordancewith this disclosure may be drawn, and in some embodiments will bedrawn, to a substantially amorphous sheet, and preferably essentiallyfree of crystalline phases, in spite of having a glass stability factor<100° C. For instance, in various embodiments the sulfide based glasshas a glass stability factor <100° C., <90° C., <80° C., <70° C., <60°C., <50° C., <40° C. and even less then <30° C. (e.g., no more than 50°C.). To prevent crystal nucleation, the time span over which the glassmaterial is heated is preferably kept to a minimum.

Draw processing of sheet 100 is suitable for yielding, in itsas-solidified state, a substantially amorphous vitreous sheet of batteryserviceable size, uniform thickness and substantially parallellengthwise edges. Consequently, it is contemplated that the vitreoussheet, as drawn (i.e., as solidified), requires little to no postformation processing (i.e., post solidification processing), other thanannealing and slicing off low quality edge portions. For instance, thedrawn solid electrolyte sheet, once formed, is annealed to removestresses, but does not require any grinding and/or polishing to bringabout the desired surface topography (e.g., a smooth liquid-likesurface). To retain the amorphous nature of the vitreous solidelectrolyte sheet once it has been drawn (e.g., essentially free ofcrystalline phases), care should be taken to avoid processes that mightexpose the sheet to temperatures which would effect crystallization, andthus the solid electrolyte sheet should not be subjected to apost-solidification heat treatment near (or above) its crystallizationtemperature (T_(x)).

Draw processing is generally used in the large-scale manufacture ofion-exchangeable flat glass, and glass strips for semiconductor anddisplay technologies. Herein, draw processing is being utilized to makehighly Li ion conductive vitreous solid electrolyte glass, and inparticular Li ion conducting sulfur-based glass sheets, including thosewith a glass stability factor less than 100° C., as are described hereinthroughout the specification.

The chemical composition of the sulfur-based solid electrolyte glasswill determine its thermal properties. Accordingly, as described above,in various embodiments the glass composition is selected to optimize itsthermal properties for formability, while retaining acceptable Li ionconductivity (>10⁻⁵ S/cm). In various embodiments the glass compositionis selected for its ability to achieve a viscosity of 10³ to 10⁸ poise,and preferably 10⁴ to 10⁷ poise, at a temperature below that at which itstarts to crystallize, while having a room temperature Li ionconductivity of no less than 10⁻⁵ S/cm, preferably no less than 10⁻⁴S/cm, and more preferably no less than 10⁻³ S/cm.

In various embodiments sulfide based glass sheet 100 is fabricated usingan overflow technique such as fusion draw, which uses a drawing tank andtakes advantage of gravity to allow molten glass to flow down theoutside surfaces of the tank, and by this expedient yields two flowingglass surfaces (i.e., two liquid streams) which are joined (by fusion)to form a single flowing sheet (i.e., a single liquid glass stream ofunbroken continuity).

In one embodiments the disclosure provides a method for making vitreoussulfide based solid electrolyte sheet 100 by fusion draw. With referenceto the fusion draw apparatus 600A in FIGS. 6A-B, a material batch of Liion conducting sulfide glass powder, which may be formed by mechanicalmilling, is heated in a melting vessel (e.g., above T_(liq)) wherefromit is caused to flow (via flow pipes 605) into a trough-like container607 in an amount sufficient to cause overflow of the fluid glass 609from both sides of the trough. The opposing flows are then combined byfusion to form a single liquid stream of unbroken continuity 100, whichmay be fed to drawing equipment (e.g., via edge rollers or glass pullingrods), for controlling the thickness of the sheet depending upon therate at which the solidified portion of the sheet is pulled away.Preferably, the major surfaces of the as-solidified glass sheet, or atleast its high quality center portion, are pristine, as they have notcontacted any part of the apparatus (e.g., the trough walls or flowpipes), and therefore may have superior surface quality. In variousembodiments, the fusion draw process may be modified to allow for thedrawing of two dissimilar glasses; for example, one optimized forcontact with lithium metal and the other optimized for a differentpurpose(s) or utility, such as contact with a positive electrode batterycell component (e.g., a lithium positive electroactive material) or aliquid phase electrolyte, or ease of processing or high conductivity.For instance, a first sulfide glass stream of unbroken continuity (e.g.,having as constituent elements: lithium, sulfur, and silicon, but devoidof phosphorous) fused to a second sulfide glass stream (e.g., having asconstituent elements: lithium, sulfur, and one or more of boron orphosphorous, but devoid of silicon).

In various embodiments, freestanding solid electrolyte sheet 100 may beformed by slot draw to yield a substantially amorphous vitreousmonolithic solid electrolyte sheet of Li ion conductingsulfur-containing glass. With reference to FIG. 6C, an apparatus 600Cfor making the freestanding sheet using a slot drawing process isillustrated. The apparatus includes i) melting vessel 660, for heatingand holding a material batch above the melting temperature; and ii) openslot 670 near the bottom of the tank and through which the batch ofglass flows by drawing to form a continuous glass sheet 100 which may beoptionally pulled through rollers 680 for shaping, and optionallytraversed into furnace 690 for an annealing heat treatment, andthereafter optionally placed through a second set of rollers 685 and/orsubjected to an edge removal process (as described above) to yield thevitreous sheet as a solid electrolyte separator or web in its final ornear final form.

Additional processing steps may be used to enhance the cooling rate,such as flowing a non-reactive fluid (e.g., dry nitrogen) over one orboth surfaces; including a warm inert fluid (i.e., above roomtemperature, 25° C.), a cold inert fluid (i.e., below room temperature,25° C.), a cryogenic fluid of nitrogen, or other inert gas over thesurface(s) of the fluid glass stream (e.g., helium or argon). Thecooling gas will generally have a very low moisture content (e.g., dryair or dry nitrogen), preferably less than 0.5%, and more preferablyultra dry nitrogen or gas devoid of oxygen, and with a dew point lessthan −50° C., and preferably less than −70° C.

In various embodiments the material batch is composed of raw precursorpowders in proper stoichiometry for making the glass (e.g., Li₂S, B₂S₃,P₂S₅, P₂O₅ and the like), and the precursor ingredients should bethoroughly blended during melting to avoid stria-like inhomogeneities,such as ream, and may be fined as necessary to mitigate bubbles.

In various embodiments the material batch is already a glass (i.e., itis a glass batch), typically in powder form. In embodiments the glasspowder batch may be made by mechanically milling precursor powders. Forinstance, material batches of sulfide glass may be prepared viamechanical milling of precursor ingredients. The milling may beperformed at room temperature for several hours (e.g., about 10 hours)using a planetary ball mill, zirconia milling media, and rotating speedsof several hundred revolutions per minute (e.g., about 500 RPM). Methodsfor processing batches of Li ion conducting sulfide glass powders usingmechanical milling are generally described in U.S. Pat. No. 8,556,197 toHama and Hayaahi, and US Patent Publication No.: 2005/0107239 to Akibaand Tatsumisago, both of which are hereby incorporated by reference fortheir disclosure of these methods. Alternatively, the batch glass may beprocessed by melt quenching precursor ingredients, followed by optionalpulverizing of the quenched blob or boule to a powder; in such instancesthe material batch is itself an already melt-processed glass.

Starting with a material batch that is already a Li ion conductingglass, as described above, has distinct advantages for drawing. Forinstance, as opposed to starting with precursor powder materials (e.g.,Li₂S and P₂S₅), the batch powder glass can be melted at lowertemperature and will generally have a lower vapor pressure when comparedto a melt derived from raw precursor ingredients. Typically, as outlinedabove, the process includes a first step of making a batch sulfide glasspowder using mechanical milling (or conventional melt/quench/grind); asecond step of heating the glass powder batch to a temperaturesufficient to allow drawing (e.g., about T_(liq)); and a third step,which is to process the molten glass to a vitreous glass sheet bydrawing as outlined above. In contrast to melting a mixture of rawprecursor ingredients, using glass powder instead is somewhatcounterintuitive as it adds a potentially costly glass making step tothe process, and, in particular, it effectively requires making theglass twice—initially as a bulk glass (optionally pulverized to apowder) and then to a vitreous sheet.

In various embodiments vitreous solid electrolyte sheet 100 is formed bypreform drawing, wherein a preform of the sulfide based solidelectrolyte glass is drawn (e.g., pulled) in length at a temperatureabove the glass transition temperature of the prefrom, to the desiredshape and size. Typically, to be drawn from a preform, it (the preform)is heated to a temperature at which it has low enough viscosity that itcan deform under its own weight. This generally occurs at around the“softening point”—typically defined as having a viscosity of about10^(7.65) poise. Upon drawing the preform, the heated section (i.e.,that part of the preform in the deformation zone) becomes a highlyviscous fluid of unbroken continuity, as it reaches a viscositytypically in the range of 10⁴-10⁶ poise.

With reference to FIG. 6D there is shown an apparatus 600D suitable forpreform drawing sulfide based solid electrolyte sheet 100. In operation,the vitreous preform 610D is heated in a deformation zone 620D and thendrawn using mechanized rollers 630D. Within the deformation zone thepreform is exposed to heat sufficient to raise its temperature aboveT_(g) but below T_(m) and preferably below T_(x), wherefrom it forms aviscous fluid stream of unbroken continuity that is drawn to yield awall structure of desired battery serviceable shape and size (e.g., asheet), the fluid stream thinning as it flows. In some embodiments it iscontemplated that the drawing apparatus includes a flow system forflowing an inert gas nearby the drawn sheet in order to speed up coolingof the pulled sheet section, the gas preferably having a very lowmoisture and oxygen content, as described above.

The resulting cross sectional shape of the formed sheet is usuallysimilar to that of the preform from which it was drawn. Preferably, thepreform has a smooth flat surface with minimal surface roughness andwaviness. In various embodiments the preform is, itself, a vitreousmonolithic construct. For instance, the preform may be made by moldingmolten glass into a rectangular bar-like shape of significant thicknessand width, and typically 10 times thicker than that desired for sheet100. For instance, to a draw a thin vitreous solid electrolyte sheet inthe range of 10 to 500 μm thick, in various embodiments the preform is arectangular bar having a thickness in the range of 200 μm to 1000 μm, awidth of 5 to 20 cm, and a length of about 30 cm to 100 cm (e.g., about5 cm wide, about 30 cm long and about 400 um thick). Methods andapparatus' for drawing a glass preform to form a substrate forsemiconductor devices and flat panel displays are described in US Pat.Pub. No.: US20070271957, US20090100874; 20150068251; all of which areincorporated by reference herein.

In various embodiments the preform may be made by dispensing a moltensulfide glass of the desired composition into a hot mold ofvitreous/glassy carbon, preferably at a temperature above T_(g) (of theglass), and, in some instances, the mold may be held at a temperatureabove T_(x), and then, given sufficient time to minimize turbulence,cooling the mold to the solidify the glass preform. By this expedient,the preform is more readily processed without voids or cracks that mightotherwise arise if cooled too rapidly. In various embodiments, thepreform may be processed via precision glass molding, or ultra precisionglass processing. Depending on the chemical composition of the sulfideglass, the material from which the mold is made can be an importantaspect of processing. The mold should be chemically compatible with theglass at high temperature, and it should also have a surface qualitycommensurate with that required of the preform itself, and thuspreferably of a smooth liquid-like surface (e.g., vitreous carbon, alsoreferred to herein and elsewhere as glassy carbon).

In various embodiments, the preform is fabricated from the melt in aglassy carbon mold (e.g., the mold is made of glassy carbon or at leastthe mold surfaces which contact the sulfide glass are made of glassycarbon). In other embodiments, the preform may be processed by melting amaterial batch of an already processed glass or its raw precursormaterials in an evacuated and sealed quartz ampoule. The furnaceemployed may be horizontal but is preferably vertical and even morepreferably a rocking furnace, which allows for mixing during heating.Once the glass has fully melted, the ampoule is held vertical for asufficient time to minimize turbulent flow, and then immersed in aquenching medium (e.g., a water bath). For instance, the furnace may bea vertical furnace with automation control for manipulating the ampoule.In various embodiments, rather than fast quench the melt, the melt maybe slow cooled (e.g., by less than 10° C. per minute) to enable thermalequilibrium throughout the entirety of the melt, and by this expedientreducing the tendency for cracking via thermal shock. The cooling rateand temperature time cycle on cooling depends on a number of factors,including the glass stability factor and crystal growth rate. In variousembodiments, especially when the glass stability factor is <100° C., themelted sulfur based glass (e.g., in the ampoule) is slow cooled to atemperature above T_(x) (e.g., >20° C., >50° C. above T_(x)) but belowT_(liq.), and then quenched below T_(g) to prevent crystallization. Forglasses having thermal stability >100° C., it is contemplated to slowcool to a temperature above T_(g) (e.g., >20° C., >50° C. above T_(g))and then quench below T_(g). Immediately following quenching, thevitreous glass preform may be annealed to remove internal stresses thatmay develop as a result of the process.

Cylindrical ampoules are commonly employed, however, the disclosurecontemplates using an elliptical or rectangular shaped ampoule, toproduce, directly from the melt/quench, a rectangular shaped vitreousbar of Li ion conducting sulfur based glass, preferably of thickness <5mm, and more preferably <1 mm thick. For instance, the preform,as-formed, is <1 mm thick and >1 cm wide, and preferably >10 cm long. Bythis expedient the preform is of the desired shape for drawing a glasssheet or ribbon. The use of a rectangular shaped ampoule improves thecooling profile across the thickness of the preform, as opposed tocylindrical ampoules, which typically have diameter 1 cm or greater. Thevarious methods described herein to produce the preform may also besuitable for batch fabrication of flat specimens by cutting the preform(e.g., via a wire saw) to a desired shape and thickness, followed bypolishing and/or controlled roughening to achieve the desired surfacequality. Typically, the sample produced in this manner will be cut alongthe width of the preform. For example, if the preform so formed iscylindrical, the flat specimens are generally circular shaped pieceswith diameter matching, or near that of, the preform itself. In thisway, a disc or rectangular flat specimen of about 1-3 cm diameter orside, may be provided for testing or use in a stacked or single layerbattery cell. Small solid electrolyte specimens may be batch produced inthis manner. In another embodiment, flat specimens may be batchprocessed by stamping molten sulfur based glass between pressing plates(e.g., vitreous carbon plates) to a desired thickness, or vitreous glassblanks (e.g., blobs or boules) of the Li ion conducting sulfur-basedglass may be precision molded as described above by heating the blanksabove T_(g) (e.g., to about or above the softening point), and moldingthe blanks to the desired shape and thickness, followed by cooling tobelow T_(g). It is also contemplated to use glass powder in place of thevitreous blanks, followed by precision molding.

In accordance with the disclosure, drawing apparatus 600A-D aregenerally enclosed in a controlled atmosphere housing or the drawing isperformed in a dry room or in a large dry box to minimize or eliminateexposure of the vitreous sulfide preform or molten sulfide glass tomoisture and/or oxygen in the air. For instance, the controlledatmosphere has less than 100 parts per million (ppm) H₂O/O₂ (e.g., nomore than 10 ppm). In various embodiments the atmosphere nearby, orinside, the melting vessel contains an inert gas partial pressure (e.g.,argon) effective to reduce volatilization and condensation of elementalconstituents, especially sulfur and phosphorous (when present), whichare prone to evaporate from the melt. To minimize the loss of volatiles,in various embodiments the inert gas pressure inside the housing orvessel is greater than 1 atm (e.g., about 2 atm or greater). In certainembodiments the melting vessel is capped with a cover plate to achievean overpressure of sulfur above the melt, for reducing volatilization.In various embodiments the inert gas is maintained at a higher pressureover the melt than the vapor pressure of sulfur at the temperature ofthe melt, or that of phosphorous when present. In various embodiments,it is contemplated that a certain amount of nitrogen gas may be combinedwith the inert gas for the purpose of incorporating nitrogen as acomponent of the sulfide glass skeleton.

The as drawn solidified sheet may be placed on a backing layer tofacilitate conveyance of the solid electrolyte sheet. In variousembodiments the backing layer also serves as interleave for protectingsurfaces when the sheet is formed continuously into a web and rolled.The backing layer may be a non-lithium ion conducting glass sheet (e.g.,a silica glass or borosilicate glass) or a polymer film (e.g., apolyester layer). Generally the backing layer does not strongly adhereto the solid electrolyte sheet, and so readily removed. In someembodiments the backing layer may be coated with a liquid layer (e.g.,an organic solvent or organic substance) that enhances adhesion butstill allows for easy removal. It is also contemplated that the backinglayer may also serve as interleave and as a polymeric separator layer(e.g., a porous or gellable polymer layer). In such embodiments theinstant separator is a combination of the polymeric separator layer andfreestanding glass sheet in a hybrid battery cell, as described in moredetail herein below, or in a solid state cell, if the polymericseparator layer is a solid polymer electrolyte in the absence of aliquid electrolyte.

In some embodiments the continuously drawn solid electrolyte sheet iscut-to-size inline with the drawing process. The cut-to-size solidelectrolyte sheets may then be stacked for storage and transport. Invarious embodiments a material interleave may be incorporated betweenadjacently stacked sheets to prevent their direct contact, or the solidelectrolyte glass sheets may by fitted with an edge-protector elementsthat serve to protect the edges of the sheet from physical damage, andmay also serve as a spacer for creating a gap between stacked or rolledsheets, as described in more detail below.

With reference to FIGS. 7A-C there is illustrated flowchartsrepresentative of various methods 700A-C of making solid electrolytesheet 100 using draw processes as described above. Methods 700A-Cinclude a first step of selecting a glass composition 705. For example,the composition may be selected for suitability to the particular drawprocess of making sheet 100 (e.g., preform draw 750A from a vitreouspreform 740A to form a vitreous glass ribbon 760A and/or melt draw 750Bfrom molten glass 740B to form a vitreous glass sheet 760B).

In various embodiments the elemental constituents are selected andadjusted to enhance thermal properties. In some embodiments thatadjustment leads to a significant reduction in conductivity (e.g., by afactor of 2, 3, 4 or 5, or an order of magnitude reduction).

In various embodiments, the mole ratios of elemental constituents areadjusted to increase the glass stability factor of the sulfide-basedglass. In various embodiments the adjustment results in a glassstability factor {T_(x)−T_(g)}≥30° C., preferably ≥50° C., and even morepreferably ≥100° C. In various embodiments the adjustment results in anincrease of the glass stability factor by at least 10° C., but with asubsequent loss in conductivity of between a factor of 2-100 (e.g., by afactor of between 2-5, 5-10, 10-20, 20-50 and 50-100), while stillretaining a conductivity ≥10⁻⁵ S/cm, and preferably ≥10⁻⁴ S/cm. Invarious embodiments, the glass stability factor increases by more than20° C., or more than 30° C., or more than 50° C.

In various methods, the step of selecting the sulfur containing glasscomposition is based on glass stability factor and conductivity; e.g.,selecting a glass composition having a glass stability factor >20° C.,or >30° C., or >40° C., or >50° C., or >60° C., or >70° C., or >80° C.or >90° C. or >100° C. and a Li ion conductivity ≥10⁻⁵ S/cm, andpreferably ≥10⁻⁴ S/cm, and more preferably ≥10⁻³ S/cm.

In various methods, the step of selecting the sulfur containing glasscomposition is based on Hruby parameter and conductivity; e.g.,selecting a glass composition having Hruby parameter >0.4, or >0.5,or >0.6, or >0.7, or >0.8, or >0.9, or >1, and a Li ion conductivity≥10⁻⁵ S/cm, and preferably ≥10⁻⁴ S/cm, and more preferably ≥10⁻³ S/cm.

In various methods the step of selecting the sulfur containing glasscomposition involves adjusting the mole percent of Li and/or S (sulfur)and/or O (oxygen) in the glass to achieve a Hruby parameter of >0.5,or >0.6, or >0.7, or >0.8, or >0.9, or >1 and a Li ion conductivity≥10⁻⁵ S/cm, and preferably ≥10⁻⁴ S/cm, and more preferably ≥10⁻³ S/cm.

In various methods the step of selecting the sulfur containing glasscomposition involves adjusting the mole ratio of Li and/or S (sulfur)and/or O (oxygen) in the glass to achieve a glass stability factorof >50° C., or >60° C., or >70° C., or >100° C. and a Li ionconductivity ≥10⁻⁵ S/cm, and preferably ≥10⁻⁴ S/cm, and more preferably≥10⁻³ S/cm.

In various methods, the step of selecting the glass composition includesreplacing a certain amount of S (sulfur) in the glass with O (oxygen),the amount sufficient to increase the glass stability factor by at least10° C. or the Hruby parameter by at least 0.1, while maintaining a Liion conductivity ≥10⁻⁵ S/cm, and preferably ≥10⁻⁴ S/cm, and morepreferably ≥10⁻³ S/cm. In various embodiments the glass stability factoris increased by at least 20° C., 30° C., 40° C., 50° C., 60° C., or 70°C. by the oxygen replacement for sulfur, while maintaining the requisiteLi ion conductivity ≥10⁻⁵ S/cm. In various embodiments the Hrubyparameter is increased by at least 0.2, 0.3, 0.4, 0.5, 0.6, or 0.7 bythe oxygen replacement for sulfur, while maintaining the requisite Liion conductivity.

In various methods, the step of selecting the glass compositionincludes: i) selecting constituent elements of the sulfur-based glass,the constituent elements comprising S (sulfur), Li (lithium), and one ormore of P (phosphorous), B (boron), Si (silicon), and O (oxygen); andii) adjusting the mole ratio of the constituent elements to maximizeviscosity at T_(liq) (i.e., the liquidus viscosity), without decreasingthe room temperature Li ion conductivity of the sheet below 10⁻⁵ S/cm,and preferably not decreasing the conductivity below 10⁻⁴ S/cm. Forexample, the maximized liquidus viscosity greater than 200 poise,preferably greater than 500 poise, more preferably greater than 1,000poise, and even more preferably greater than 3,000 poise. In preferredembodiments, the maximizing step does not increase the ASR, as measuredagainst Li metal, to a value greater than 200 Ω-cm², and preferably notgreater than 100 Ω-cm², or greater than 50 Ω-cm², or greater than 20Ω-cm².

In various methods, the step of selecting the glass compositionincludes: i) selecting constituent elements of the sulfur-based glass,the constituent elements comprising S (sulfur), Li (lithium), and one ormore of P (phosphorous), B (boron), Si (silicon), and O (oxygen); andii) adjusting the mole ratio of the constituent elements to maximize theglass stability factor {T_(x)−T_(g)}, without decreasing the roomtemperature Li ion conductivity of the sheet below 10⁻⁵ S/cm, andpreferably not decreasing the conductivity below 10⁻⁴ S/cm. For example,maximizing the glass stability factor to a value greater than 50° C.,and preferably greater than 100° C. In preferred embodiments, themaximizing step does not increase the ASR against lithium metal to avalue greater than 200 Ω-cm², and preferably not greater than 100 Ω-cm²,or greater than 50 Ω-cm², or greater than 20 Ω-cm².

Continuing with reference to FIGS. 7A-C, once the Li ion conductingsulfur containing glass composition is selected 705, the raw precursormaterials (e.g., Li₂S, SiS₂, and P₂S₅ powders) 710 are processed. Withreference to methods 700A-B, as illustrated in FIGS. 7A-B, theprocessing steps involve forming a vitreous preform 730A from the rawprecursor materials, or melting the raw precursor materials 730B formaking the vitreous solid electrolyte sheet by melt drawing. In method700C the process involves the extra step of making a glass batch 720Cfrom the raw precursor materials, and then processing the glass preformor drawing a sheet from the twice-melted glass. In various embodiments,the batch glass formed in step 720C may be processed by melt/quenchingthe raw material precursors or by mechanical milling. The re-melting orformation of a vitreous preform from a batch glass, regardless of how it(the batch glass) is formed, allows better control of processingvariables, including minimizing loss of volatile constituents.

In various embodiments continuous solid electrolyte sheet 100 (e.g., asheet of vitreous Li ion conducting sulfur-containing glass) issufficiently long and robust when flexed to be configurable as avitreous web of Li ion conducting glass. In various embodiments the webis sufficiently flexible to be wound (e.g., on a spool) and thussuitable as a source/supply roll for downstream (R₂R) or roll-to-sheetprocessing of discrete cut-to-size sheets and or battery cellcomponents. Preferably, the vitreous solid electrolyte web hassufficient surface quality and thickness uniformity that it requires nopost solidification grinding and/or polishing, and even more preferablydoes not require removal of low quality peripheral edge portions.

In various embodiments the continuous web has bending-radius ≤100 cm,and preferably ≤50 cm, more preferably ≤30 cm, even more preferably ≤20cm, and yet even more preferably ≤10 cm, or ≤5 cm, or ≤2 cm, and thuscan be wound as such without fracture. In various embodiments the spoolor drum on which the web is wound has diameter between 100-200 cm; or50-100 cm; or 20-50 cm; or 10-20 cm; or 5-10 cm; or 1-5 cm; or 0.5-1 cm;for example, a spool having a diameter no greater than 20 cm, or nogreater than 10 cm, or no greater than 5 cm.

The vitreous web is typically of sufficient length to serve as a sourcefor multiple discrete solid electrolyte separator sheets (i.e.,cut-to-size), or the web may serve as a long substrate sheet for makingmultiple cell components (e.g., multiple electrode assemblies ormultiple sub-electrode assemblies). Typically, the length of the web issufficient for making many multiples of such said components (e.g., atleast 5, at least 10, or at least 20). In various embodiments the lengthof the solid electrolyte web of vitreous Li ion conducting sulfide glassis more than 20 cm, or more than 50 cm, or more than 100 cm, or morethan 500 cm, or more than 1000 cm. Discrete solid electrolyte separatorsheets, of predetermined length and width, are usually cut-to-size fromthe web by a laser (i.e., by laser cutting).

In various embodiments, the as-fabricated web may be referred to hereinas a mother-web when having a high quality center portion and lowerquality edge portions, which are sliced off by laser cutting, typicallyinline, and then followed by rolling to form a supply roll.

When making a lithium metal electrode assembly or subassembly, thevitreous web may serve as a substrate for depositing the lithium metalor tie-layer in an intermittent fashion, to form periodic sections ofcoated and uncoated regions (e.g., by using a mask or maskingtechniques). Alternatively, discrete separator sheets or discretetie-layer coated substrate laminates may be cut-to-size from the web,followed by lithium metal deposition.

In various embodiments roll processing of the web is inline with solidelectrolyte sheet fabrication (e.g., the drawing process). Withreference to FIG. 8 , there is illustrated a sheet to roll fabricationsystem 800 for processing a vitreous web of solid electrolyte glass 100Win the form of a continuous roll. Sheet to roll fabrication system 800includes solid electrolyte sheet drawing apparatus 810 (e.g., melt drawor preform draw apparatus 600C or 600D respectively, such as a fusiondraw apparatus, a slot draw apparatus, or a redraw/preform drawapparatus) configured inline with roll processing apparatus thatincludes one or more drive mechanisms 823 (e.g., a pair of opposingcounter rotating rollers), guide rollers 828, and take-up spool 826 forwinding the inorganic vitreous solid electrolyte glass web into acontinuous roll 100R. Preferably, the counter rollers, which aregenerally motor-driven, are positioned to contact a peripheral edgeregion of the as-drawn solid electrolyte sheet or edge-protectors, andby this expedient the major area portion of the solid electrolyte sheet(e.g., the high quality center portion) is maintained in a pristinesurface state condition (i.e., untouched). Driven by the rotatingrollers, solid electrolyte ribbon (long sheet) 100W is typicallyconveyed along one or more guide rollers (e.g., roller 828) beforeengaging with take-up roll 826. The web of solid electrolyte glass 100Wmay be conveyed in an unsupported fashion, or the apparatus may includea support mechanism for supporting the moving sheet as it is conveyedtoward the take-up roll, and/or into one or more processing stages 850(850 i, 850 ii, 850 iii, 850 iv). Typically, solid electrolyte web 100Wis caused to traverse through a furnace or hot zone stage 850 i forannealing the glass sheet prior to engaging with the take-up roll forwinding. The processing stages may include a slitting stage 850 ii witha cutting device (e.g., a laser cutter) configured to remove low qualityedge portions. Other stages are contemplated, including a stage forconfiguring a protector element along the lengthwise edges of the solidelectrolyte sheet 850 iii and/or material layer deposition stages 850 ivfor coating the surface of solid electrolyte glass web 100W with atie-layer and/or a current collector layer and/or a lithium metal layer,as described in more detail herein below with respect to making a web ofelectrode sub-assemblies and/or a web of lithium electrode assemblies.

To keep the surfaces of the vitreous web from directly contacting eachother, interleave 804 (i.e., a self-supporting material layer forprotecting the web surfaces) may be wound together with the web viainterleave supply roll/take off-roll 812, interleaf 804 interposedbetween layers of the glass web. Care should be taken in the properselection of the interleaf, and in particular embodiments the majoropposing surfaces of interleave material layer 804 are exceptionallysmooth (e.g., the interleave may be an organic polymer layer such aspolyolefin or polyester layer). Also contemplated is the use ofedge-protector elements, which, as described above, protect the edges ofthe solid electrolyte sheet against physical damage, and may also serveas a spacer between sheet layers when the web is wound on a spool, andby this expedient, the high quality center portion of the solidelectrolyte sheet is kept in a pristine surface state (i.e., untouchedby a foreign solid surface). The use of edge-protectors may circumventthe need for an interleaf, and in various embodiments the edge-protectorelement is multi-functional in that it can be used downstream as asealing component in an electrode assembly or as a spacer in a batterycell.

When the web is a continuous sulfide based solid electrolyte sheet,sheet to roll system 800 is typically contained inside an enclosure (notshown) substantially devoid of moisture, and in certain embodimentssubstantially devoid of oxygen, as described above for the drawingapparatus housings. In various embodiments, the roll apparatus is housedin a dry room of exceptionally low moisture content or in a dry box withvery low moisture and oxygen content (e.g., <10 ppm, and preferably <5ppm).

In an alternative embodiment sheet 100 may be fabricated as a nearlyflawless monolithic vitreous sheet of a sulfide based solid electrolyteglass by making use of capillary forces. The method is based on thefabrication of the sheet as a thin film, a sheet or a ribbon from asulfide glass melt that infiltrates or is injected into a narrow gapbetween two smooth plate surfaces provided by polished glassy carbon,polished metal, polished and coated (in particular, anodized) metal,polished glass with a higher melting point than that of the sulfideglass, pyrolytic graphite or other materials. The obtained vitreoussheet can be used “as is” or as a pre-form for a subsequent drawingoperation.

The plate materials of choice are chemically stable to the sulfide glassmelt and do not exhibit reactive wetting. Another requirement to theplate material and surface quality is dictated by necessity to separatea formed sulfide glass film from the plate surface without damaging thefilm. Thus, the sulfide glass of choice does not stick to the polishedplate surface. In a preferred embodiment, two glassy-carbon plates witha mirror-like surface finish form the gap.

Glass is melted in a crucible and poured onto a smooth horizontal ortilted plate (i.e., smooth plates), or melted directly on the limitedarea of the plate surface next to its edge. Another smooth plate isplaced on top of the first one, adjacent to the molten glass.Alternatively, molten glass is poured into a gap between two verticalplates. The width of the narrow gap between the plates is in the rangeof 5-1 mm and is fixed with spacers. In some embodiments, glass ismelted under vacuum to avoid formation of gas bubbles due to gases beingtrapped within the bulk of molten glass.

The glass fabrication procedure consists of four stages: i) glassmelting—temperature of glass is increased above Tm (glass meltingpoint); ii) gap infiltration—temperature of glass melt and plates ismaintained above Tm; iii) cooling—temperature of glass melt and platesis brought below Tg (glass transition temp); iv) glass separation.

All the operations are performed in the atmosphere of inert gas or inthe dry air. In one embodiment (illustrated in FIG. 9 ), the intrinsiccontact angle of molten glass on the plate material is less than 90° andthe molten glass is drawn into the narrow gap between two horizontal ortilted plates due to capillary forces. In this embodiment, the distancethat the molten glass infiltrates in the narrow gap between the twosmooth horizontal plates is governed by Washburn's equation. Thedistance is directly proportional to the square roots of the gap widthand the surface tension of molten glass in processing atmosphere and isinversely proportional to the square root of molten glass dynamicviscosity. In an alternative embodiment, the plates are tilted at anangle less than 90° (less than vertical) instead of being placedhorizontally, and the component of the force of gravity parallel to theplate surface aids the capillary force in driving the molten glass intothe gap.

In a different embodiment (illustrated in FIG. 10A), the intrinsiccontact angle is less than 90°, the plates are placed vertically and themolten glass is poured into the gap from above. In a modification ofthis embodiment, additional pressure is applied to the molten glass inthe downward direction with a piston or with compressed inert gas. Here,the force of gravity, the capillary force and the external force appliedto the melt are all acting in the downward direction and are aiding theinfiltration of the gap by the molten glass.

Alternatively, the intrinsic contact angle is less than 90°, the bottomedges of the vertical plates are submerged into the molten glass and themolten glass infiltrates the gap due to the capillary force acting inthe upward direction. In a modification of this embodiment, additionalpressure is applied to the free surface of the molten glass in thedownward direction with a piston (illustrated in FIG. 10B) or withcompressed inert gas (illustrated in FIG. 10C). In an alternativeembodiment, the process is scaled up by using a long crucible withmultiple pairs of plates being submerged into molten glass.

In another embodiment (illustrated in FIG. 9 ), the intrinsic contactangle is greater than 90° and an external pressure greater than thecapillary force is applied to the molten glass with a fluid-dispensingdevice with a piston or with compressed inert gas in order to forcemolten glass into the narrow gap between two horizontal (or tilted)plates.

In a different embodiment (illustrated in FIG. 10A), the intrinsiccontact angle is greater than 90°, the plates are placed vertically andthe molten glass is poured into the gap from above. The molten glassinfiltrates the gap in the downward direction due to the force ofgravity counteracting the capillary force acting in the upwarddirection. In a modification of this embodiment, a piston or compressedinert gas applies additional pressure to the molten glass in thedownward direction.

If the intrinsic contact angle is much greater than 90° and exceeds acertain threshold value determined by the plate surface roughness, themelt contacts the plate surfaces only in a limited number of points(composite wetting), making the glass separation operation easier, butpossibly affecting the smoothness of the formed glass surface. Even atlower contact angle values above 90°, spontaneous dewetting can occurdue to various surface defects.

In another embodiment, after forming the glass electrolyte film andseparating it from both plates, either one or both film surfaces areadditionally melted to eliminate surface flaws and defects.

According to the Hagen-Poiseuille equation, the pressure required forinfiltration of a narrow gap is directly proportional to dynamicviscosity of the glass melt and to the infiltration distance and isinversely proportional to the fourth power of the gap width. In someembodiments, in order to reduce the force required to achieve reasonableinfiltration times, the glass melt viscosity is reduced by heating theglass to temperatures 10-50, 50-100, 100-300° C. above the glass meltingpoint, T_(m).

In an alternative embodiment sheet 100 may be fabricated by particlecompaction followed by surface melting. For instance, with reference toFIG. 4G-H, the particles (i.e., powder particles), typically prepared bymechanical milling, are pressed together (e.g., at a temperature aboveT_(g)) to form a tape, and this is followed by heating at least one orboth major surfaces of the tape to bring about a surface meltingcondition which is sufficient to dissolve the powder inter-particleboundaries within the confines of the treated (i.e., melted) surfacelayer, effectively forming a vitreous stratum that defines the firstprincipal side surface. The vitreous stratum is typically formed byflash heating the tape surface (e.g., via a laser or hot inert gas) tocause melting, and then quickly cooling the surface, e.g., by flowing aninert gas. Preferably, the vitreous stratum is formed on the surfacewithout touching a foreign solid body. When incorporated in a batterycell or a lithium electrode assembly, the vitreous stratum disruptspowder inter-particle pathways residing within the interior of thesheet, preventing them from reaching the first principal side surface,and preferably the stratum is of sufficient mass to turn down dendrites.Preferably, the vitreous stratum has a liquid-like surface (as describedabove), whereas the interior bulk of the sheet, composed of pressedpowder particles, may be rife with particle boundaries and internalvoids, and thus highly undesirable, but unavoidable from a powdercompact. With reference to FIG. 4G, in embodiments it is contemplatedthat both first and second principal sides are surface melted andquenched to form a sandwich structure of a powder particle compactbetween two vitreous strata. However, it is also contemplated that onlya single side of the tape is surface melted and thus the sheet aparticle compact having a first principal side surface (e.g., 101A)defined by a vitreous stratum with a liquid-like surface, and the otherprincipal side surface composed of a powder compact. In variousembodiments the pressed powder compact (or tape) is made by hot pressingunder vacuum or helium to enhance the dissolution of voids and lessenthe concentration of micropores and/or nanopores in the bulk of thesheet.

In alternative embodiments, discrete wall structure 100 or a glasspreform for drawing sheet 100 may be processed using a melt quenchmethod that forms, as an initial step, a vitreous glass block or bar(e.g., rectangular or cylindrical), such as by pouring the melt from acrucible into a mold or melting a raw material batch of the glass in anevacuated and sealed quartz ampoule. Once solidified upon cooling, thebar is typically annealed and cut to a desired wall thickness, and/orsliced widthwise/lengthwise to yield the desired shape and areadimension (e.g., using a diamond blade, or wire saw, or laser cutter).Once cut, the surface of the as-cut wall structure may be subjected topolishing steps (e.g., fire polishing) to achieve a desired surfacefinish (e.g., liquid-like with R_(a) as defined above), preferably ofoptical quality. Other methods contemplated for making and/or processingsheet 100 include variations of the float glass method, updrawing thesheet, and rolling methods, such as hot rolling a vitreous glass sheetas it cools from the molten state. For instance, it is contemplated thatprecision glass molding (e.g., ultra-precision glass pressing) may beused to form a discrete wall structure or a preform for downstreamdrawing of a continuous sheet or web. The molding process includesloading a vitreous/glass blank of desired composition into a moldingtool, heating up the mold (e.g., using infrared lamps), and uponreaching the working temperature (e.g., above T_(m), or between T_(g)and the softening point of the glass), closing the mold to form avitreous glass construct. With reference to preform drawing of sheet100, the aforesaid melt/quench crucible method or precision glassmolding techniques may be useful processes for making the vitreouspreform, especially precision glass molding. The precision glass moldingprocess may also be suitable for batch fabrication of flat sheets nomore than 100 um thick, with circular, square or rectangular formfactor.

With reference to FIG. 6E in alternative embodiments it is contemplatedthat Li ion conducting solid electrolyte sheet 100 or a mother sheetthereof is made by applying a melt of the Li ion conducting glass onto afluid bed to form a vitreous sheet of Li ion conducting glass; themolten glass sheet 667 solidifying on the surface of the fluid bed 665,and thereafter removed from the bed to yield freestanding vitreous sheet100. In various embodiments the as-solidified vitreous sheet, formed assuch, may serve as a mother sheet that is sliced and cut to yielddiscrete solid electrolyte ribbons of battery serviceable size. Invarious embodiments, the composition of the fluid bed is selected to besubstantially non-reactive with the molten glass sheet. However, theinvention is not limited as such, and in other embodiments it iscontemplated that the molten glass sheet reacts in contact with thefluid bed to effect a solid crust layer which does not adhere stronglyto the solidified vitreous glass sheet, or may be removed in adownstream process, including sand blasting or chemically reacted away,and/or removed by mechanical grinding/polishing. In various embodimentsthe fluid bed is itself a molten material layer (e.g., a molten metalsuch as tin, or a metal/semi-metal alloy, or a molten salt). In yetother embodiments the bed on which the molten glass is applied andsolidified onto, is itself a solid. In various embodiments the solid bedis an amorphous metal or amorphous graphite (e.g., vitreous carbon) or apolished metal, or a non-reactive glass having T_(g) greater than themelt temperature of the sulfide glass.

In various embodiments the aforesaid solid electrolyte glass sheets,including those processed by melt draw, preform draw, or meltquench/cut, may be subjected to a post fabrication treatment, e.g.,flattening and/or polishing steps (e.g., fire polishing), to perfect thesurface topography (e.g., to minimize waviness and/or surfaceroughness). Preferably the glass sheet, after post fabricationprocessing, has flatness <5 μm, and more preferably ≤1 μm; waviness <5.0μm, and preferably ≤1.0 μm; thickness variation ±5 μm, and preferably±0.2 μm; and an average surface roughness of R_(a)<1.0 um, preferably<0.5 um, more preferably R_(a)<0.2 μm (e.g., R_(a)≤0.05 μm or R_(a)≤0.05μm), and yet even more preferably R_(a)≤0.01 μm. In various embodiments,solid electrolyte sheet 100 achieves one or more of the aforesaidproperties (i.e., flatness, smoothness, uniform thickness) in its virginstate as a solid.

In various embodiments freestanding solid electrolyte sheet 100 servesas a substrate for the formation of a lithium metal electrode assembly.As described in more detail herein below, the assembly is composed ofsolid electrolyte sheet 100 having an intimate solid-state interfacewith a lithium metal layer. In various embodiments, prior to forming thesolid-state interface, it is useful to fabricate what is termed hereinan electrode subassembly, which is effectively a substrate laminatecomposed of solid electrolyte sheet 100 coated with a material layerthat serves to enhance interface function.

With reference to FIGS. 11A-B, there is illustrated electrodesubassembly 1100A-B, which, in accordance with the present disclosure,generally serves as a component for making a standalone lithium metalelectrode assembly, and in some embodiments may be incorporated directlyinto a battery cell, also of the present disclosure. As illustrated,subassembly 1100A-B is a freestanding substrate laminate of solidelectrolyte sheet 100 covered in direct contact by material layer 1101,which provides a surface for creating an electrochemically efficientinterface with a lithium metal layer during the making of a standalonelithium metal electrode assembly or during the course of charging in abattery cell.

Material layer 1101 may be characterized as having interior surface 1101i adjacent to and in direct contact with surface 101A of solidelectrolyte sheet 100, and exterior/exposed surface 1101 ii opposing theexterior environment about the subassembly. Typically, material layer1101 is significantly thinner than solid electrolyte sheet 100 on whichit is coated, formed on or adhered to. In various embodiments materiallayer 1101 or a layer portion thereof is a transient layer thateffectively disappears (e.g., by alloying) once a lithium metal layer isapplied or deposited onto it.

As mentioned above electrode subassembly 1100A-B is a standalonecomponent for making a lithium metal electrode assembly or battery cellof the present disclosure. However, the electrode subassembly by itselfis not a capacity-bearing electrode, and thus does not containelectroactive material (e.g., lithium metal) for providing ampere-hourcapacity to a battery cell. Accordingly, electrode subassembly 1100A-Bhas exceptional component shelf life and handle-ability formanufacturing.

With reference to FIG. 11A, in various embodiments electrode subassembly1100A is a bi-layer laminate of material layer 1101 (a single layer,typically of uniform composition) coated onto solid electrolyte sheet100. With reference to FIG. 11B, in various embodiments, subassembly1100B is composed of more than two layers; for instance, material layer1101 may itself be a multilayer of two or more material layers disposedon first principal side surface 101A of sheet 100 (e.g., 1101 a atie-layer in direct contact with solid electrolyte sheet 100, and secondlayer 1110 b a current collector layer in direct contact with thetie-layer).

In various embodiments material layer 1101 is a chemically functionaltie-layer coating for creating an electrochemically efficient interfacebetween sheet 100 and a lithium metal layer, and may also provide someprotection against damage during storage and handling. Accordingly, thetie layer is of suitable composition and thickness to enhance bonding.In particular embodiments the tie-layer reactively alloys with Li metalon contact to form an electrochemically operable interface. Thetie-layer is preferably a transient layer, which transforms andessentially disappears upon the formation or deposition of lithium metalon its surface. In various embodiments the tie-layer is thin enoughand/or the lithium layer is of sufficient mass (i.e., thickness) tocompletely dissolve the tie layer (e.g., via an alloying reaction), andpreferably the elements of the tie-layer are in such small amount andfully dispersed throughout the lithium metal layer to be insignificant.

In various embodiments protective tie-layer 1101 is a coating of a metalor semi-metal suitable for forming an electrochemically operableinterface between a lithium metal layer and solid electrolyte sheet 100,and, in particular, an electrochemically efficient interface for platingand striping lithium metal in a battery cell. In various embodiments,the tie-layer is a metal or semi-metal such as Al, Ag, In, Au, Sn, Si,or the like, or an alloy or inter-metallic combination of metals orsemi-metals capable of alloying or being alloyed by lithium metal oncontact.

In various embodiments tie-layer 1101 is a metal or semi-metal coatingdeposited by physical vapor deposition (e.g., by evaporation) onto firstprincipal side surface 101A of sheet 100. Tie-layer 1101 is a transientfilm sufficiently thin to be effectively completely dissolved by lithiummetal on contact, and preferably atomically dispersed throughout, thelithium metal layer. In various embodiments tie-layer 1101 is of acomposition and thickness to fully alloy with lithium metal on contactat room temperature, and in some embodiments heat may be applied tofacilitate alloying and atomic diffusion. In various embodiments thetie-layer thickness is in the range of 0.05 to 5 μm and more typicallybetween 0.05 to 1 μm (e.g., about 0.05 μm, or 0.1 μm, 0.2 μm, 0.3 μm,0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, or about 1.0 μm, or 2.0μm, 3.0 μm, 4.0 μm or about 5.0 μm).

The tie-layer provides a subassembly surface for mating the solidelectrolyte sheet to a lithium metal layer (e.g., extruded lithiumfilm), when forming a lithium electrode assembly or battery cell of thepresent disclosure. In particular, by reactively alloying with Li metal,the tie layer facilitates formation of an electrochemically operableinterface. Moreover, the tie-layer is a transient material layer in thatonce the lithium metal layer is applied or formed, the tie-layereffectively disappears as it alloys with Li.

With reference to FIG. 11A, various embodiments the lithium metal layeris applied onto exterior tie-layer surface 1101 ii during fabrication ofa lithium metal electrode assembly (e.g., a lithium foil hot rolled ontothe tie-layer). In other embodiments the lithium metal layer is formedby electrochemically plating lithium metal adjacent to interiortie-layer surface 1101 ii during initial charging of a battery cell inwhich the electrode subassembly is incorporated. Whether formedelectrochemically in a battery cell or applied or coated to form alithium metal electrode assembly, lithium metal interacts with thetie-layer to form an intimate electrochemically operable interfacebetween the as-formed or applied lithium metal layer and first principalside surface 101A of solid electrolyte sheet 100.

With reference to subassembly 1100B in FIG. 11B, in various embodimentsmaterial layer 1101 is a multilayer (e.g., a bi-layer) devoid of Limetal. In various embodiments bi-layer 1101 is composed of tie-layer1101 a in direct contact with first principal side surface 101A of sheet100, and current collecting layer 1101 b in direct contact with thetie-layer. The tie-layer sandwiched between sheet 100 and currentcollecting layer 1101 b. In various embodiments the tie-layer may beevaporated onto the solid electrolyte sheet 100 followed by applying acurrent collecting layer 1101 b directly onto the tie-layer 1101 a. Inother embodiments it is contemplated that the tie-layer may beevaporated onto the current collector layer, and the multi-layer, soformed, applied onto the sheet. Multiple tie-layer coatings are alsocontemplated herein, such as one or more additional tie-layer coatingsdisposed between tie-layer 1101 a and current collecting layer 1101 b.For instance, an additional tie-layer may be utilized to enhance andimprove the Li metal interface in direct contact with current collectinglayer 1101 b.

In alternative embodiments it is contemplated that the currentcollecting layer may be applied directly onto sheet surface 101A, in theabsence of a tie-layer.

The current collector layer may be a thin metal foil, or a thin metalfilm on a polymer substrate, or a coating applied directly onto sheetsurface 101A, or indirectly via a tie-layer. For example a thin Cu or Nifoil, or a laminate of a Cu film on a polyethylene terephthalate (PET)substrate. The current collector should be a material layer that issubstantially unreactive in contact with Li metal and of sufficientelectronic conductivity to provide effective current collection,typically a metal (e.g., Cu or Ni).

In various embodiments, the current collecting layer is preferablysignificantly thinner than solid electrolyte sheet 100 (e.g., ≤⅕ or ≤1/10 the thickness of sheet 100), and preferably no thicker than 10 μm.In various embodiments the current collecting material layer is <20 μmthick, and typically <15 μm, and more preferably ≤10 um, and even morepreferably ≤5 μm thick (e.g., between 10 to 5 μm thick; for exampleabout 5 μm, or 4 μm, or 3 μm, or 2 μm, or 1 μm thick).

In various embodiments, electrode subassembly 1100A serve as a substratecomponent for making a standalone lithium metal electrode assembly ofthe present disclosure. In other embodiments electrode subassembly 1100Amay be directly incorporated into a lithium battery cell as a lithiumfree negative electrode, completely devoid of Li metal, as described inmore detail below.

In various embodiments, the electrode subassembly is fabricated byprocessing material layer 1101 (e.g., tie-layer and/or current collectorlayer) directly onto glass web 100W (as described above), the glass webserving as substrate for the laminate. In various embodiments, materiallayer 1101 may be coated or adhered to the glass web in a continuous orintermittent fashion, and the web laminate referred to herein as anelectrode subassembly web.

With reference to FIG. 12A, there is illustrated a sheet to rollfabrication system 1200A for processing an electrode sub-assembly web1200W in the form of a continuous source roll 1200R. In variousembodiments sub-assembly web 1200W is formed by coating a web of Li ionconducting glass 100W with a tie-layer and/or current collector layer1101 downstream of, and inline with, drawing solid electrolyte sheet 100as a continuous web of glass 100W, as described above with reference toFIG. 8 . The tie-layer and/or current collector layer is coated onto theweb via processing stage 850 iv (as shown in FIG. 8 ) or coating stage850 iv as shown in FIG. 12A. In various embodiments, coating 1101 is amulti-layer of a tie-layer 1101 a and a current collector layer 1101 b,and in such embodiments, coating stage 850 iv is understood toincorporate more than one coating unit for each of the layers.

In various embodiments, fabrication of an electrode subassemblyinvolves: i) forming a continuous web of the instant solid electrolytesheet 100W via drawing apparatus 810 (as described above); ii)traversing the as-formed/as-drawn continuous solid electrolyte web 100W(e.g., in the form of a self-supporting layer) through a series ofoptional stages (annealing 850 i, slicing 850 ii, and edge protecting850 iii), and there from into coating stage 850 iv, wherein the firstprincipal side surface of web 100W, preferably pristine, is coated witha tie layer and/or current collector layer as described above (e.g., viavacuum evaporation); and iii) winding the coated solid electrolyte webvia take-up spool 1206, to form an electrode subassembly source roll1200R suitable for storage, transportation and downstream R₂Rmanufacturing or roll-to-sheet processing of lithium electrodeassemblies and/or battery cells.

To achieve inline processing, coating unit(s) of stage 850 iv should bedisposed in a differentially pumped chamber (not shown), wherein the tielayer (e.g., a thin aluminum or silver layer) and/or current collectorlayer (e.g., copper layer) is deposited. Similar to winding a continuousweb of solid electrolyte sheet, winding of sub-assembly web 1200W toform continuous roll 1200R optionally involves interposing an interleave1204 to prevent contact between adjacent surfaces. Alternatively, theedge-protector elements on web 100W, when present, can serve as aspacer.

As described above, material layer 1101 (e.g., tie-layer and/or currentcollector) may be formed as a continuous coating onto solid electrolyteweb 100W (thus forming a continuous laminate of coated web 100W, or,with reference to FIG. 12B, layer 1101 may be coated intermittently toyield periodic well-defined sections of coated and uncoated regions (asillustrated). Discrete electrode subassemblies are formed from thecoated regions, and may be excised from sub-assembly web 1200W bycutting along the widthwise and/or lengthwise dimension of the web,preferably laser cut. With the cutting operation performed within theconfines of uncoated region 1205, discrete/individual electrodesubassemblies 1200Z are excised without having to cut or score through atie-layer and/or current collector layer.

With reference to FIG. 12C, in other embodiments, fabrication ofsubassembly source roll 1200R involves R₂R processing of a continuousweb of solid electrolyte sheet 100W, which has already been configuredas supply roll 806, and is used herein as a source roll for makingsubassembly web 1200W and ultimately roll 1200R. The process involvesthe steps of unwinding source roll 800R to expose the first principalside surface of vitreous web 100W, conveying/traversing the continuoussolid electrolyte sheet (i.e., web 100W) into coating stage 850 iv, asdescribed above. Electrode subassembly web 1200W, thus formed, is thenwound on spool 1206 to yield supply roll 1200R for downstream R₂Rmanufacture of a lithium electrode assembly, or battery cell. Similar tothat described above, in various embodiments material interleave 1204may be incorporated into the roll to prevent direct contact betweenadjacent layers of the web. Guide rollers 1208 i-ii, and interleavesupply roll/take off-rolls 1212 i-ii provide mechanisms for removing andintroducing interleaves 804 and 1204 respectively.

In accordance with the present disclosure, electrode subassembly 1100A-B(see FIG. 11 ), as described above, or sheet 100 (absent of a tie-layercoating) may be utilized as a Li ion conducting solid electrolyteseparator layer in a lithium metal electrode assembly of the presentdisclosure.

With reference to FIG. 13A, standalone electrode assembly 1300 is alithium metal electrode assembly composed of solid electrolyte sheet 100serving as a substrate for lithium metal component layer 1320, which iscomposed of lithium metal layer 1310 and optional current collectinglayer 1312. By use of the term standalone with respect to lithium metalelectrode assembly 1300 it is meant that the electrode assembly is adiscrete cell component devoid of positive electroactive material, andthat it exists as a freestanding component outside of a battery cell.

The electrode assembly generally takes the shape and size of the solidelectrolyte sheet from which it is made. In various embodiments, thelithium metal electrode assembly is rectangular shaped having lengthwiseand widthwise dimensions and associated edges. In particularembodiments, when the solid electrolyte sheet is ribbon-like, thelengthwise dimension is significantly longer than the widthwisedimension; for instance, the rectangular shaped lithium metal electrodeassembly (itself ribbon-like) has a length to width area aspect ratiosubstantially matching that of the solid sheet(s) from it is formed. Forexample, the Li metal electrode assembly having an area aspect ratiogreater than 2, greater 3 or greater than 5 (e.g., an area aspect ratioof about 2, 3, 4, 5, 6, 7, 8, 9 or about 10). In various embodiments thearea aspect ratio is at least 2 and the length of the Li metal electrodeassembly is ≥5 cm, ≥10 cm, ≥15 cm, or ≥20 cm.

In various embodiments, standalone lithium metal electrode assembly 1300contains at least a sufficient amount of lithium metal to support therated capacity of the cell in which it is disposed, and, in particular,is sufficient to match or exceed the rated area ampere-hour capacity ofthe positive electrode. For instance, in various embodiments thepositive electrode may have an area capacity of about 1 mAh/cm², about1.5 mAh/cm², about 2 mAh/cm², about 2.5 mAh/cm², about 3 mAh/cm², about3.5 mAh/cm², about 4 mAh/cm², about 4.5 mAh/cm² or about 5 mAh/cm²; andLi metal layer 1310 has a respective thickness of at least 5 μm, 7.5 μm,10 μm, 12.5 μm, 15 μm, 17.5 μm, 20 μm, 22.5 μm, or at least 25 μm.

In other embodiments, the amount of lithium metal in standaloneelectrode assembly 1300, prior to incorporation into a battery cell, isinsufficient to support the rated capacity of the cell. For instance,the rated capacity of the cell is about 50% greater than the Li metalcapacity in the standalone electrode assembly, or about 100% greater, orabout 150% greater, or about 200% greater, or about 250% greater, orabout 300% greater, or about 350% greater, or about 400% greater, orabout 450% greater, or about 500% greater.

In various embodiments the amount of lithium metal in the assembly priorto incorporation into the battery cell is insufficient to support thedischarge capacity. In various embodiments, lithium metal layer 1310 isless than 15 μm thick (e.g., between 5 to 10 μm) and the rated areacapacity of the battery cell into which the lithium metal electrodeassembly is ultimately intended is >3 mAh/cm², or >4 mAh/cm², or >5mAh/cm², or >6 mAh/cm², or >7 mAh/cm²; or the lithium metal layer 1310is less than 20 μm (e.g., between 5 to 20 μm; e.g., about 10 μm) and therated area capacity of the battery cell into which the lithium metalelectrode assembly is ultimately intended is >4 mAh/cm², or >5 mAh/cm²,or >6 mAh/cm², or >7 mAh/cm². In various embodiments the positiveelectrode of the cell into which the electrode assembly is to beemployed has an area capacity between 1 mAh/cm² to 2 mAh/cm² and thelithium metal thickness in the standalone assembly is less than 5 μm; orthe positive electrode has an area capacity ≥3 mAh/cm² (e.g., about 3mAh/cm², about 3.5 mAh/cm², about 4 mAh/cm², about 4.5 mAh/cm², or about5 mAh/cm²) and the lithium metal thickness is ≤10 μm; or the positiveelectrode has an area capacity ≥5 mAh/cm² (e.g., about 5 mAh/cm², about6 mAh/cm², or about 7 mAh/cm²) and the lithium metal thickness is ≤20μm.

In particular embodiments the amount of Li metal on the surface of solidelectrolyte sheet 100, in assembly 1300, is scant relative to the ratedcapacity of the positive electrode or cell into which it is to beemployed. For example, the Li metal layer in the electrode assembly isless than 1 μm thick, and the rated capacity of the cell is greater than1 mAh/cm².

In various embodiments lithium metal layer 1310 is deposited by physicalvapor deposition (PVD), such as evaporation or sputter deposition. Forinstance, when Li metal layer 1310 is an evaporated layer, it typicallyhas thickness in the range of 5 to 30 μm (e.g., about 5 μm, about 10 μm,about 15 μm, about 20 μm, about 25 μm, or about 30 μm. In certainembodiments Li metal layer, evaporated, has a thickness of less than 1μm, and is used primarily as a bonding layer for attaching a currentcollector to surface 101A of sheet 100. The evaporated lithium metal maybe deposited directly onto sheet 100, or via a transient tie-layer onsurface 101A.

Li metal layer 1310 may be attached to solid electrolyte sheet 100 (or asubassembly of a tie-layer coated sheet) by adhering a lithium foil orlithium film to first principal side surface 101A of sheet 100 (e.g.,via lamination, such as by hot rolling). In various embodiments, Limetal layer 1310 may be an extruded Li foil, or Li film on a currentcollecting substrate, with the thickness of the lithium metal layerabout 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, or50 μm thick). Preferably Li metal layer 1310 has a fresh surface. Forexample, a Li foil that is freshly extruded just prior to placing itonto solid electrolyte sheet surface 101A. Exposure of the freshlyextruded foil to the ambient environment should be minimized prior tocontacting the solid electrolyte sheet or tie layer coating (whenpresent). If not freshly extruded, the lithium foil may be treated(e.g., bristle scrubbed) to create freshly exposed surfaces which arethen immediately mated to first principal side surface 101A of sheet 100(e.g., directly onto the sulfide glass surface or the tie layer surfaceif a subassembly is employed).

By use of the term “fresh” when referring to an extruded lithium foil ora freshly scrubbed lithium metal surface, it is meant that thepost-extrusion/post-scrubbing exposure time to the ambient environmentis sufficiently limited to prevent forming a prohibitively thickresistive film on the lithium metal surface (typically the resistivefilm some combination of oxide, hydroxide and carbonate). Generally, theambient environment in which the foil is extruded or scrubbed has amoisture content <100 ppm, preferably <50 ppm, and more preferably <10ppm; and preferably the oxygen content is also low (e.g., <100 ppm,preferably <50 ppm, and more preferably <10 ppm).

Regardless of the extremely low moisture and oxygen content of theambient environment in which the Li metal layer may be formed ortreated, in order to be considered herein as fresh (e.g., freshlyextruded or freshly treated), the exposure time between extrusion (orsurface treatment) and placing/positioning the extruded lithium foilonto solid electrolyte sheet 100 should be limited to minutes, typically<10 minutes, and preferably <1 minute and more preferably <30 seconds.In embodiments, it is contemplated that the time period betweenextruding (or surface scrubbing) and placing the Li foil onto the solidelectrolyte sheet surface is about 1 minute-3 minutes, or less than 60seconds, or less 30 seconds, or less than 20 seconds, or less than 10seconds (e.g., within about 10 or 5 seconds of extrusion/scrubbing).

In various embodiments, surface 101A may be intentionally transformed(via a roughening step) from having a smooth surface to a roughersurface for the purpose of enhancing interfacial contact with a Li metalfilm or foil; for example, by abrasive scrubbing or bristle blasting(e.g., spraying grit onto the surface). For instance, in variousembodiments the first principal side surface is transformed to increaseits roughness by a factor of 10 or more; for example, from having aninitial smooth surface with R_(a)<0.05 to a rougher surface withR_(a)>0.1 or from R_(a)<0.1 μm to R_(a)>1 μm.

In a particular embodiment a self-supporting current collector layer isadhered to the first principal side surface of the freestanding vitreoussolid electrolyte sheet by roller laminating the layer to the sheetwhile forming a thin lithium metal bonding layer on the surface of thecurrent collector immediately prior to, or simultaneous with, thelaminating step (e.g., the bonding layer no more than 1 μm thick). Invarious embodiments, the lithium metal bonding layer is of sufficientthickness to also serve as a seed layer for enhancing uniformity ofelectrochemically deposited Li metal in a battery cell (e.g., thebonding layer about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 0.8, 0.9 or 1.0 μmthick).

For example, with reference to FIG. 13B, standalone lithium metalelectrode assembly 1300 may be formed by rolling or placing currentcollecting layer 1312 directly onto solid electrolyte sheet 100 incombination with evaporating lithium metal or spraying Li metal vaporbetween it (1312) and sheet 100. This technique provides a mechanism forbonding a discrete self-supporting current collecting layer to the solidelectrolyte sheet. For example, the discrete current collecting layer1312 a thin Cu foil or a laminate of a Cu metal coated on a polymericsubstrate. In an alternative embodiment, not shown, it is contemplatedthat current collector layer 1312 may have a pre-existing lithium metallayer already present on its surface prior to laminating to the solidelectrolyte in the presence of Li metal vapor.

With reference to FIG. 13C there is illustrated another process formaking lithium metal electrode assembly 1300, by pressure spreading a Limetal block 1355 onto first principal side surface 101A of sulfide glasssheet 100. The spreading operation, which may be performed with heat,breaks apart the resistive film to effect immediate contact of freshlithium surfaces to the solid electrolyte sheet. Lithium metal block1355 is sized relative to the total area of solid electrolyte sheet 100and the desired thickness of the lithium metal layer to be formed,preferably the as-spread lithium metal layer is of a substantiallyuniform thickness (e.g., about 5 um, or about 10 um, or about 15 um orabout 20 um, or about 25 um, or about 30 um, or about 35 um, or about 40um, or about 45 um or about 50 um). In some embodiments, as-spreadlithium metal layer 1310 is a thin layer of about 5 to 20 um, and athicker Li foil is then subsequently adhered to its surface to impart ahigher Li metal capacity to the electrode assembly.

While standalone Li metal electrode assembly 1300 comprises a lithiummetal layer, the disclosure also contemplates a lithium-free electrodein the form of an electrode subassembly, as described above andillustrated in FIG. 13D. In such embodiments, lithium metal layer 1310is formed inside a battery cell by electrochemically plating lithiummetal onto a tie-layer and/or current collector layer adjacent to firstprincipal side surface 101A. In various embodiments the assembly isconsidered substantially lithium-free when the amount of Li metal in thestandalone electrode assembly is scant (e.g., a seed layer less than 1μm thick).

With reference to FIG. 13E there is illustrated what is termed herein anencapsulated standalone lithium metal electrode assembly 1300E. Invarious embodiments encapsulated assembly 1300E is composed of lithiummetal component layer 1320 encapsulated between a first solidelectrolyte sheet 100 and an opposing backplane component 1330, both ofwhich are substantially impervious to liquids they may come into contactwith during manufacture, storage and operation, and preferablynon-reactive with said liquids. Lithium metal component layer 1320comprises a Li metal layer in direct contact with sheet 100, and one ormore optional layers, as described in more detail below, which areadjacent to backplane 1330. Solid electrolyte sheet 100 and backplanecomponent 1330 respectively define the major exterior opposing surfacesof the Li metal electrode assembly. By use of the term encapsulate whenreferring to the lithium metal component layer of the assembly it ismeant that the solid electrolyte sheet and backplane component are incontiguous mechanical force contact with the lithium metal componentlayer. Accordingly, as a result of the encapsulation, lithium metalcomponent layer 1320, and in particular the lithium metal layer, may besubjected to stacking pressure when incorporated in a battery cell.

In some embodiments encapsulated lithium metal electrode assembly 1300Eis double-sided and the backplane component is a second solidelectrolyte sheet (e.g., substantially identical to the first solidelectrolyte sheet). In other embodiments, backplane component is not aLi ion conductor, and the encapsulated lithium metal electrode assemblyis referred to herein as single-sided; for instance, the backplane maybe a substantially inert material layer or an electronically conductivematerial layer with current collector functionality. By use of the termsingle-sided or double-sided it is meant with respect to whether one orboth sides of the electrode assembly supports Li ion through transport(via electrical migration).

With reference to FIG. 13F, in some embodiments encapsulated electrodeassembly 1300F is double-sided, and the backplane component is a secondsolid electrolyte sheet (designated as 100-2). When double-sided,lithium metal component layer 1320 is typically a tri-layer composed ofcurrent collecting layer 1312 disposed between first and second lithiummetal layers, 1310-1 and 1310-2 respectively.

In various embodiments, the encapsulated double-sided lithium metalelectrode assembly is fabricated by providing a first and a second Limetal electrode assembly as described above with reference to FIG. 13A,and combining the two assemblies between a single current collectinglayer 1312, or when the two assemblies are provided each with their owncurrent collecting layer, they may be combined by placing one on theother (i.e., current collector to current collector).

With reference to FIG. 13G, in other embodiments, the backplanecomponent is not a Li ion conductor, and assembly 1300G, encapsulated,is single-sided. In various embodiments, when single-sided, backplanecomponent 1330 may be an inert material component layer, orelectronically conductive with current collector functionality. Forinstance, inert backplane component 1330 may be a polymeric layer (rigidor flexible) or when electronically conductive, the backplane may be amulti-layer of at least one polymer layer providing an exterior surfaceof the assembly and an electronically conductive metal layer inelectronic communication with the lithium metal layer (e.g., in directcontact with the lithium metal layer or in direct contact with a Cucurrent collecting layer).

In various embodiments the encapsulated assembly may be edge sealedalong the lengthwise and/or widthwise dimensions. When entirely sealedalong its edges, the assembly is considered sealed and preferablyhermetic, and the lithium metal layer(s) are isolated from the externalenvironment.

With reference to FIG. 13H, in various embodiments the edge seals (e.g.,lengthwise edges as shown) may be effected by fusion or pinch sealingthe peripheral edges of solid electrolyte sheet 100-1 to that of solidelectrolyte sheet 100-2. The direct bonding between sheets 100-1 and100-2 may be performed with heat and/or pressure. For instance byheating the periphery of one or both sheets above T_(g) (e.g., using alaser to heat the edges), and more typically above the softeningtemperature, and pressing/compressing (i.e., pinching) to effect theseal, or heating above T_(m) and allowing the sheets to fusion seal toeach other.

In other embodiments, as shown in FIG. 13I, the edge seal(s) may includea discrete sidewall component 1335 interfacing with solid electrolytesheet 100-1 and backplane component 1330. The discrete sidewallcomponent may be an inert polymer or a glass wire placed along thelengthwise edge and then heat/fusion sealed to sheet 100 and thebackplane component 1330 (e.g., a second solid electrolyte sheet). Whenthe edge is sealed made with a fusion sealable glass, it is generallynot a Li ion conductor (e.g., a non-conducting sulfide glass). In otherembodiments the discrete sidewall component 1335 may be an epoxy seal;e.g., the epoxy applied as a viscous fluid along the lengthwise edge(s),and then cured (e.g., with heat).

In various embodiments the lengthwise edges of the assembly may besealed as described above, and the widthwise edges sealed likewise(e.g., all the edges fusion sealed). In other embodiments, the widthwiseedges, which are generally of significantly shorter length, may besealed in a different manner. For instance, in a double sidedencapsulated electrode assembly, the lengthwise edges of the solidelectrolyte sheets may be pinch or fusion sealed to each other (asdescribed above), and the widthwise edges sealed via a discrete sidewallcomponent, such as an epoxy seal or a non-conductive glass or polymericwire seal.

With reference to FIG. 13J, in various embodiments discrete sidewallcomponent 1335 is edge-protecting element 105 as illustrated in FIG. 1G,which as described above may be a polymeric bracket that protects thesheet against edge cracking. When the assembly is double-sided, theedge-protecting elements may be adhered to each other, directly orindirectly. For example, directly heat/fusion bonded to each other (whenelement 105 is heat/fusion sealable) or otherwise adhered to each otherusing a discrete bonding material, such as an epoxy.

With reference to FIGS. 13H-J, in an alternative solid-state negativeelectrode assembly embodiment, lithium metal component layer 1320 isreplaced with an alternative electroactive component layer comprising anelectroactive material having a potential within about 1V of Li metal(e.g., intercalatable carbon). In various embodiments, the alternativenegative electroactive component layer is formed as a powder particlecomposite comprising: i) particles of intercalatable carbon, silicon orsome combination thereof as the electroactive material of the componentlayer; ii) particles of sulfide glass/glass-ceramic powder for ionicconductivity within the layer; and iii) optionally an amount of a carbonblack particles as a diluent for enhancing electronic conductivity. Thesolid-state particle composite layer 1320 may be laminated directly tosolid electrolyte sheets 100-1 and 100-2 (as shown in FIG. 13H/13I) andedge sealed, as described above, to yield a sealed double-sidedsolid-state negative electrode assembly. As described in more detailbelow, this alternative sealed solid-state negative electrode assemblyis particularly beneficial for use in a hybrid battery cell whencombined with a high voltage Li ion intercalating positive electrode(e.g., having a potential vs. Li metal that is greater than 3.5V, andpreferably greater than 4V or 4.5V).

In other embodiments the lithium metal electrode assembly has what istermed herein an unconstrained backplane architecture, wherein theassembly is configured to allow the lithium metal layer(s) of theassembly to undergo electrochemical plating and striping reactions in anunconstrained fashion, wherein the backplane of the Li metal layer(i.e., its second major surface) is not encapsulated by the backplanecomponent, and thus the lithium metal layer is unconstrained along thenormal direction and free to expand and contract without pressure alongits thickness direction during lithium metal plating/stripping (when thecell is being charged/discharged). By this expedient the lithium metallayer is not subjected to stacking pressure in a battery cell.

With reference to FIG. 13K there is illustrated single-sided lithiummetal electrode assembly 1300K having unconstrained backplanearchitecture. In various embodiments, the assembly is sealed along itslengthwise edges or it may be entirely sealed about all edges, andpreferably hermetic, as described above. Assembly 1300K includes solidelectrolyte sheet 100 encapsulating first major surface of lithium metallayer 1310 in direct contact, and discrete side wall component 1335interfacing with solid electrolyte sheet 100 and backplane component1330—effectively sealing the lengthwise edges of the assembly. Notably,the assembly is configured to effect gap 1350 between backplane 1330 andlithium metal layer 1310, and to maintain a gap over the course ofoperation of a battery cell in which the assembly is employed; the sizeof the gap will generally increase during discharge (as lithium metal isstripped) and decrease during charge (as Li metal is plated). Inaccordance with this embodiment, lithium metal layer 1310 is notsubjected to stacking pressure in the battery cell, and, in particular,external pressure (mechanical force) is not exerted on layer 1310 bybackplane component 1330, and thus configured to freely expand andcontract (in thickness) during charge and discharge. In variousembodiments lithium metal layer 1310 has current collector 1312 on itssecond major surface, and flexible conductive element 1313 (e.g., ametal wire or strip) tethered to the current collector or lithium metallayer for providing electronic communication to electrode assemblyterminal 1315 (e.g., a metal connector), the terminal for providingelectrical power to/from an external device.

With reference to FIG. 13L there is illustrated double-sided assembly1300L having an unconstrained backplane architecture in accordance withthe present disclosure. In various embodiments assembly 1300L may befabricated by combining a first single sided assembly (designated1300K-1) and a second single sided assembly (designated 1300K-2), withoptional sharing of a single backplane component, as illustrated in FIG.13K.

The afore described electrode assemblies are freestanding battery cellcomponents, which, entirely self-supporting, may be manufactured, storedand/or handled (by machine manipulation or otherwise) as a standalonecomponent absent, for example, an opposing electrode (e.g., a positiveelectrode) or a battery cell housing. The assemblies have also beenembodied in the absence of liquid electrolyte, and are thereforecompletely solid-state (i.e., fully solid-state Li metal electrodeassemblies). Preferably, the electrode assemblies are sufficiently thinand flexible to be suitable for use in wound or folded battery cellconstructions. In various embodiments, the electrode assembly is sealed(i.e., entirely edge sealed), and thus hermetic, and therewith whenincorporated in a battery cell having a liquid electrolyte, the assemblyprotects the lithium metal layer(s) (or more generally electroactivelayers) from contact with catholyte (i.e., the liquid electrolyte incontact with the positive electrode). In alternative embodiments, it iscontemplated that the sealed electrode assembly (e.g., double-sided) isnot a solid-state negative electrode assembly, and includes aporous/gellable separator layer disposed between sheet 100 andelectroactive component layer 1320, the gel layer impregnated withliquid electrolyte (i.e., anolyte).

In accordance with another aspect of the disclosure, there is provided acontinuous web of lithium electrode assemblies.

With reference to Li metal electrode assembly manufacturing process1400A illustrated in FIG. 14A, in various embodiments lithium electrodeassemblies are fabricated inline with drawing of the continuous web ofsolid electrolyte sheet 100W, the overall process including one or moreof the following post-solidification processing stages of: i) annealing850 i; ii) edge removal 850 ii; iii) edge protecting 850 iii; iv)coating stage 850 iv for creating tie-layer 1101; v) lithium depositionstage 1492 for depositing (e.g., evaporating or hot rolling) lithiummetal layer 1310 directly onto web 100W or onto tie-layer coating 1101when present; and vi) winding the as-formed lithium electrode assemblyweb 1400W onto take-up roll 1406, to form lithium electrode assemblysource roll 1400R, with optional interleave 1404; and slitting the web,lengthwise and/or widthwise, to form individual/discrete lithiumelectrode assemblies (e.g., lithium electrode assembly 1300 asillustrated in FIG. 13A).

In various embodiments lithium metal layer 1310 is deposited via stage1492 using physical or chemical vapor deposition (e.g., via evaporationof lithium metal in a differentially pumped chamber). In otherembodiments, stage 1492 is a laminating stage wherein lithium metallayer 1310 (e.g., a lithium metal foil) is laminated directly onto web100W (e.g., via hot rolling). In other embodiments, stage 1492 includesapparatus for applying a current collecting layer directly to thesurface of web 100W, as illustrated in FIG. 13B.

As illustrated in FIG. 14B, in various embodiments lithium metal layer1310 is deposited or laminated intermittently to form well definedlithium coated regions 1310 and uncoated regions 1405, and by thisexpedient, lithium electrode assembly web 1400W comprises a multitude ofdiscrete electrode assemblies, which may be excised by laser cuttingwithin the confines of the uncoated regions. In various embodiments, thediscrete electrode assemblies are excised from web 1400W inline withfabrication process 1400A but prior to any downstream rolling.

As illustrated in FIG. 14C, in other embodiments, lithium electrodeassembly web 1400W may be R₂R processed from a continuous source roll ofsolid electrolyte web 100R (as shown in FIGS. 3A-B and FIG. 8 ) or fromsource roll 1200R of subassembly web 1200W (as shown in FIGS. 3A-B andFIGS. 12A-C), whereby web 100W/1200W is unwound from its source roll100R/1200R, traversed into lithium stage 1492, coated or laminatedtherein with lithium metal layer 1310. Typically the lithium is coatedin an intermittent fashion to yield discrete lithium coated and uncoatedregions. Thereafter, discrete lithium electrode assembly components maybe excised from web 1400W by cutting across uncoated region 1405 (e.g.,with a laser cutter), or wound onto spool 1422 to form source roll1400R.

In various embodiments, lithium deposition stage 1492 involveslaminating a fresh lithium metal foil (e.g., freshly extruded) onto web100W/1200W. In various embodiments Li metal layer 1310 is unwound from asource roll 1442 and surface scrubbed to expose fresh lithium metalsurfaces, and then bond laminated via hot rollers 1475 to web100W/1200W. In other embodiments, the lithium metal deposition stageinvolves evaporating Li metal onto web 100W or 1200W. In an alternativeembodiment stage 1492 involves unwinding a roll of a current collectinglayer (e.g., Cu foil) and bonding the Cu foil directly to web 100W or1200W using lithium vapor as described above with reference to FIG. 13B.

With reference to FIG. 15 , in various embodiments the electrodeassembly is a standalone positive electrode assembly, wherein a positiveelectroactive component layer is encapsulated on both major surfaces byfirst and second solid electrolyte sheets of the present disclosure.Specifically, positive electrode assembly 1500 is double-sided andcomposed of first and second solid electrolyte sheets 100-1 and 100-2edge sealed via discrete sidewall component 1335 (e.g., as describedabove in various embodiments for the lithium metal electrodeassemblies). Positive electroactive material component layer 1560 istypically a tri-layer of current collecting layer 1564 (e.g., aluminumor stainless foil) coated on both sides by an electroactive materiallayer 1562-1 and 1562-2, which, in various embodiments has a lithium ionintercalation compound as its electroactive material (e.g., an oxidesuch as e.g., LiCoO₂, LiMn₂O₄, LiNiO, LiNi_(0.33)Mn_(0.33)Co_(0.33)O₂,LiNi_(0.8)Co_(0.15)Al_(0.05)O₂). In various embodiments, positiveelectrode assembly 1500 includes liquid electrolyte in contact withelectroactive layer 1562, and present in its pores. In variousembodiments, as shown, the assembly includes a first and second porousseparator layer or gel electrolyte layer (designated as 1570-1 and1570-2, respectively), which, impregnated with liquid electrolyte,provide positive separation between the electroactive layers and theiropposing solid electrolyte sheets. Preferably the assembly is wellsealed around its edges, and the liquid electrolyte is prevented fromseeping out (e.g., hermetically sealed). In alternative embodiments thepositive electrode assembly may be single-sided and the second solidelectrolyte sheet replaced with an inert or current collecting backplanecomponent impermeable to the liquid electrolyte and preferablynon-reactive (e.g., a polymer and/or metal layer). When double-sided, itis contemplated that positive electrode assembly 1500 may be edge sealedwith a fusion or pinch seal as described above, rather than using adiscrete sidewall component. In some embodiments, a solid polymerelectrolyte may be used to effect positive separation between theelectroactive layers and the opposing solid electrolyte sheets. In thisway, the positive electrode assembly may be devoid of a liquidelectrolyte.

With reference to FIG. 16A there is illustrated a lithium battery cell1600A in accordance with the present disclosure, the battery cellcomprising a cell laminate 1601 including solid electrolyte sheet 100disposed between positive electrode 1660 and negative lithiumelectroactive layer 1610, for example a Li metal layer such as thosedescribed above with reference to layer 1310.

In various embodiments the combination of lithium electroactive layer1610 (e.g., an evaporated or extruded lithium metal layer) and solidelectrolyte sheet 100 (e.g., a vitreous sulfide glass) is incorporatedin the battery cell as standalone Li metal electrode assembly 1300, asdescribed with reference to FIGS. 13A-L, or more generally as astandalone negative electrode assembly.

Cell laminate 1601 is generally disposed in a cell housing (not shown).In various embodiments the cell laminate is sufficiently flexible to befoldable and more preferably windable, and thereby cell 1600A may be ofa wound prismatic or wound cylindrical construction, or a foldableconstruct disposed in a pouch-like housing (e.g., a multilayer laminatematerial). Battery cell 1600A may be made by: i) combining layers: 1610,100, and 1660, to form laminate 1601; ii) winding or folding thelaminate into a shaped construct (e.g., cylindrical or prismatic); iii)placing the shaped construct into a rigid or flexible housing such as amultilayer laminate pouch or rigid container; and then iv) sealing thepouch or container. When a liquid electrolyte is employed in the cell,it is typically dispensed after the laminate is disposed in the cellhousing.

In various embodiments, laminate 1601 is wound or folded with radius ofcurvature ≤3 cm, ≤2 cm, ≤1 cm, ≤0.5 cm, or ≤0.25 mm without fracturingsolid electrolyte sheet 100. In various embodiments cell 1600A includesa spindle about which laminate 1601 is wound, the spindle typicallyhaving diameter ≤6 cm, ≤4 cm, ≤2 cm, ≤1 cm, or ≤6 mm.

In various embodiments, positive electrode 1660 includes positiveelectroactive layer 1662 disposed on current collecting layer 1664(e.g., a metal foil, such as aluminum, nickel, stainless steel or thelike). In various embodiments positive electrode 1660 may be solid-state(i.e., devoid of a liquid electrolyte) or it may contain a liquidelectrolyte, typically impregnated in the pores of electroactive layer1662. In various embodiments positive electroactive layer 1662 is alithium ion intercalation layer composed of a lithium ion intercalationcompound as the electroactive material. When combined with a liquidelectrolyte, positive electroactive layer 1662 is typically porous, andwhen solid-state the layer is preferably dense (e.g., a highly compactedparticle composite). Particularly suitable lithium ion intercalationcompounds include, for example, intercalating transition metal oxidessuch as lithium cobalt oxides, lithium manganese oxides, lithium nickeloxides, lithium nickel manganese cobalt oxides, lithium nickel cobaltaluminum oxides (e.g., LiCoO₂, LiMn₂O₄, LiNiO,LiNi_(0.33)Mn_(0.33)Co_(0.33)O₂, LiNi_(0.8)Co_(0.15)Al_(0.05)O₂ and thelike) or intercalating transition metal phosphates and sulfates (e.g.,LiFePO₄, Li₃V₂(PO₄)₃, LiCoPO₄, LiMnPO₄, and LiFeSO₄) or others (e.g.,LiFeSO₄F and LiVPO₄F), as well as high voltage intercalating materialscapable of achieving cell voltages versus lithium metal in excess of 4.5Volts.

In various embodiments the electroactive material of layer 1662 is ofthe conversion reaction type including transition metal oxides,transition metal fluorides, transition metal sulfides, transition metalnitrides and combinations thereof (e.g., MnO₂, Mn₂O₃, MnO, Fe₂O₃, Fe₃O₄,FeO, Co₃O₄, CoO, NiO, CuO, Cu₂O, MoO₃, MoO₂, and RuO₂).

In various embodiments the electroactive material of layer 1662 iselemental sulfur and/or lithium polysulfide species, typically dissolvedin a non-aqueous liquid electrolyte. In such said embodiments, thebattery cell may be considered a lithium sulfur battery. Generally, whenmaking use of dissolved electroactive speices (polysulfides orotherwise), electroactive layer 1662 is an electron transfer medium thatfacilitates electrochemical redox during discharge and charge, and, assuch, is typically a porous metal or porous carbonaceous layer.

Continuing with reference to FIG. 16A, in some battery cell embodiments(especially those of the solid-state type described in more detailherein below), positive electroactive layer 1662 is disposed adjacent toand in direct contact with second principle side surface 101B of solidelectrolyte sheet 100, and, in some embodiments, the positiveelectroactive material directly contacts surface 101B. However, in otherembodiments, an additional Li ion conductive material layer (not shown),such as a solid organic or inorganic Li conducting layer, may beincorporated between solid electrolyte sheet 100 and positiveelectroactive layer 1662. For instance, the additional material layermay be a solid polymer electrolyte layer, such as a polyethylene oxide(PEO) or a PEO like layer, or block copolymer electrolyte infused with alithium salt (e.g., as described in U.S. Pat. No. 8,691,928 incorporatedby reference herein), or it may be an inorganic Li conducting layer(e.g., PVD coated onto the second side surface of solid electrolytesheet 100). The solid polymer electrolyte layer (not shown) can providebenefit as it pertains to chemical compatibility at the interface withthe positive electroactive layer. Solid-state positive electroactivelayer 1662 may be a particle composite of electroactive particles andsulfide glass/glass ceramic particles, and in some embodiments, may beengineered to effect a surface that is absent electroactive material, asdescribed in more detail herein below.

In various embodiments battery cell 1600A is of the hybrid cell type,having a fully solid-state negative electrode (e.g., a fully solid-stateand sealed lithium metal electrode assembly) and a positive electrodeimpregnated with a liquid electrolyte, and thus the positive electrodenot solid-state. In other embodiments cell 1600A is fully solid-state,and thus entirely devoid of liquid phase electrolyte. In various fullysolid-state cell embodiments, solid electrolyte sheet 100 serves as thesole solid electrolyte separator layer between negative lithiumelectroactive layer 1610 (e.g., a lithium metal layer) and positiveelectrode 1660.

In various embodiments cell 1600A is not fully solid state, and thusincludes a liquid phase electrolyte. In some embodiments the liquidphase electrolyte is a common electrolyte present throughout the celland contacts both the positive electrode (e.g., positive electroactivelayer 1662) and negative lithium electroactive layer 1610 (e.g., lithiummetal layer). By use of the term “common electrolyte” it is meant thatthe liquid electrolyte in contact with the negative electroactive layeralso contacts the positive electroactive layer, and thus the “commonliquid electrolyte” is continuous throughout cell laminate 1601. Acommon liquid electrolyte yields a rather unusual and counterintuitivecell construction, in that it employs both a solid-state separatorcomposed of solid electrolyte sheet 100 (preferably devoid of throughporosity) and a continuous liquid phase electrolyte that contacts bothpositive electroactive layer 1662 and negative electroactive layer 1610.In fact, solid electrolyte sheet 100 may be used as a Li ion conductingsolid electrolyte separator layer in an otherwise conventional lithiumion cell, with the solid electrolyte sheet providing through conductionfor Li ions while preventing short circuiting by lithium dendrites andproviding protection against thermal runaway. In some embodiments, sheet100 serves as a direct replacement for the micro-porous polymericseparator layer or gel electrolyte layer commonly employed inconventional lithium ion cells (e.g., Celgard® or the like), and in suchembodiments battery cell 1600A includes a common liquid electrolyte butis explicitly devoid of a porous separator layer or gel layer. Forexample, battery cell 1600A may be embodied by positive electrode 1660having porous positive electroactive layer 1662 comprising a lithium ionintercalation compound (e.g., LiCoO₂) and porous negative electroactivelayer 1610 having as its electroactive material a lithium ionintercalation material or alloying material (e.g., intercalatable carbonor silicon or some combination thereof). Moreover, while this disclosurecontemplates that the common liquid electrolyte may exist primarily inthe pores of the positive and negative electroactive layers, it is notlimited as such, and in some embodiments the cell may include one ormore porous separator layers (e.g., a micro-porous polymer layer such asa porous polyolefin or the like) or gel electrolyte layer positionedbetween solid electrolyte sheet 100 and electroactive layer(s) 1610and/or 1662. When incorporated in a cell having a common liquidelectrolyte, solid electrolyte sheet 100 is preferably substantiallyimpervious to the common liquid electrolyte, but the invention is notnecessarily so limited.

In various embodiments the battery cell of the present disclosure is ofa hybrid cell construction: composed of a solid-state and sealednegative electrode assembly, as described above, and a positiveelectrode impregnated with a liquid electrolyte. When referring to anelectrode assembly as solid-state, it is meant that the assembly doesnot contain liquid, and in particular that the electroactive material ofthe assembly does not contact liquid phase electrolyte.

With reference to FIG. 16B, in various embodiments battery cell 1600B isof a hybrid cell construction, and solid-state negative electrodeassembly 1640B is a sealed solid-state negative electrode assembly, suchas those illustrated in FIGS. 13H-I. In particular embodiments theliquid electrolyte is present in the pores of positive electroactivematerial layer 1662, and is chemically compatible in direct contact withsecond side surface 101B of sheet 100. To prevent the liquid electrolytefrom contacting lithium metal layer 1310, solid electrolyte sheet 100should be free of through porosity and impermeable to the liquidelectrolyte, and therefore substantially impervious.

In various embodiments, and in particular when the solid electrolytesheet is a sulfide based glass, the liquid phase electrolyte isnon-aqueous, and exceptionally dry, meaning that it is has very lowmoisture content, preferably less than 20 ppm, more preferably less than10 ppm, and even more preferably less than 5 ppm. Non-aqueous liquidelectrolytes suitable for use herein include solutions of organicsolvent(s), such as carbonates (e.g., DMC, EEC, PC, EC), and a lithiumsalt dissolved therein (e.g., LiBF₄, LiClO₄, LiPF₆, LiTf and LiTFSI;where Tf=trifluormethansulfonate;TFSI=bis(trifluoromethanesulfonyl)imide), as well as liquid electrolytesbased on ionic liquids, as are known in the battery field arts.

In various embodiments, cell laminate 1601B includes separator layer1670 disposed between sealed negative electrode assembly 1640B andpositive electrode 1660B; the separator layer typically a porousmaterial layer or gel electrolyte layer that is impregnated with thenon-aqueous liquid electrolyte. For instance, separator layer 1670 aporous organic polymer, such as a porous polyolefin layer (e.g.,microporous). Separator layer 1670 provides positive separation betweensecond principal side surface 101B of solid electrolyte sheet 100 andpositive electroactive material layer 1662. The separator layer mayprovide various benefits. In particular embodiments, layer 1670 enablesthe combination of a solid electrolyte sheet and a positiveelectroactive material layer that are chemically incompatible in directcontact with each other. In other hybrid cell embodiments, thecomposition of solid electrolyte sheet 100 is chemically compatible indirect contact with the positive electroactive material of layer 1662,and laminate 1601B may be absent layer 1670, and sheet 100 and layer1662 disposed in direct contact. Cell laminate 1601B may be wound orfolded and incorporated into a cell housing. Thereafter, the liquidphase electrolyte dispensed into the cell, wherein it contacts positiveelectrode 1660B, and in particular layer 1662, but does not contactlithium metal of layer 1320, as it is isolated inside the sealedelectrode assembly.

In particular embodiments cell 1600B is composed of: i) electroactivelayer 1310—a lithium metal layer; ii) solid electrolyte sheet 100—asubstantially impervious sheet of vitreous Li ion conductingsulfur-based glass sheet; iii) positive electroactive material layer1662—composed of a lithium intercalation material, such as an oxide(e.g., LiCoO₂, LiMn₂O₄, LiNiO, LiNiMnCoO₂ or the like) or phosphate(e.g., LiFePO₄); iv) optional separator layer 1670—a porous polymer orgel, impregnated with a liquid phase electrolyte; v) a non-aqueousliquid phase electrolyte present in the pores of layers 1662 and 1670,and chemically compatible with second principal side surface 101B ofsulfide based solid electrolyte glass sheet 100. For instance, lithiummetal layer 1310 and solid electrolyte sheet 100 incorporated into cell1600B as a sealed solid-state lithium metal electrode assembly.

In various embodiments hybrid cell 1600B may include a thin porousceramic layer, typically <10 μm thick, disposed between solidelectrolyte sheet 100 and electroactive layer 1662. The thin porousceramic layer may be formed as a coating on the surface of firstprincipal side 101B, or on the surface of electroactive layer 1662. Insome embodiments the thin porous ceramic layer may be coated on thesurface of separator layer 1670. In various embodiments the porousceramic layer may be a composite of ceramic particles held together withan organic binder. In various embodiments the ceramic particles may be aceramic powder not conductive of Li ions (e.g., alumina powderparticles), or conductive of Li ions (e.g., a Li ion conductivegarnet-like or LATP ceramic powder particles), or some combinationthereof. In embodiments the porous ceramic layer has thickness of aboutSum, or about 4 um or about 3 um or about 2 um. In some embodiments theporous ceramic layer may provide positive separation between solidelectrolyte sheet 100 and positive electroactive layer 1662, in theabsence of a porous or gel separator layer 1670.

With reference to FIG. 16C there is illustrated a fully solid-statebattery cell 1600C in accordance with various embodiments of thisdisclosure. The cell includes solid-state positive electrode 1660C;solid-state negative electrode 1640C; and Li ion-conducting solidelectrolyte sheet 100 serving as separator. In some embodimentscomponents 1660C/1640C/100 are incorporated into the cell as discretematerial layers.

In other embodiments, separator sheet 100 and negative/positiveelectrodes 1640C/1660C are incorporated in the cell as standalonecomponents (e.g., standalone solid-state negative electrode assembly oras a standalone solid-state positive electrode assembly.

Solid-state positive electrode 1660C includes positive electroactivelayer 1662C and current collector layer 1664C. In various embodimentselectroactive layer 1662C is a composite of positive electroactivematerial combined with solid electrolyte material of composition similarto, or the same as, that of vitreous sulfide glass sheet 100. Withoutlimitation, particle composite layer 1662C may be fabricated bycompaction or tape casting of positive electroactive particles, Li ionconducting sulfide glass or sulfide glass-ceramic particles, andoptionally electronically conductive particles for enhancing electronicconductivity, such as a carbonaceous material, (e.g., carbon blackparticles). In particular embodiments the positive electroactiveparticles are Li ion intercalating compounds, as described above (e.g.,metal oxides). In various embodiments, the component particles ofcomposite layer 1662C are uniformly distributed throughout theelectroactive layer. In some embodiments, composite layer 1662C isengineered to have a surface that is defined by compacted Li ionconducting sulfide particles, and substantially devoid of electroactiveparticles and electronically conductive additives.

In particular embodiments positive electroactive material layer 1662C isof the lithium ion intercalation type, and preferably has potential vs.Li metal that is >2 Volts, such as, but not limited to those describedabove with reference to positive electroactive layer 1662 in FIG. 16A(e.g., transition metal oxides such as LiCoO₂, LiMn₂O₄, LiNiO,LiNiMnCoO₂ or the like, or phosphates such as LiFePO₄). In someembodiments the positive electroactive intercalation material has anamorphous atomic structure, which can be advantageous for enhancinguniform plating and striping of lithium metal due to the diffuse natureof the ionic current emanating from an amorphous layer, and in someembodiments layer 1662C is a dense layer, solely composed of amorphousLi ion intercalation material (e.g., an amorphous vanadate depositeddirectly onto surface 101B of solid electrolyte sheet 100).

Solid-state negative electrode 1640C is composed of negativeelectroactive material layer 1610C, which may be a lithium metal layeras described above, with optional current collecting layer 1612C. Invarious embodiments lithium metal layer 1610C and solid electrolytesheet 100 are incorporated into cell 1600C as a standalone solid-statelithium metal electrode assembly in accordance with various embodimentsof the present disclosure. In alternative embodiments, negativeelectroactive layer 1610C is not a lithium metal layer, but rather alayer comprising electroactive material having a potential near that oflithium metal, such as, but not limited to, intercalatable carbon,silicon or a combination thereof. In such said embodiments,electroactive layer 1610C may be a particle compact or tape cast layerof negative electroactive material particles (e.g., intercalatablecarbon) combined with solid electrolyte particles of composition similarto, or the same as, that which constitutes sheet 100. Negativeelectroactive layer 1610C may further contain electronically conductivediluents (such as high surface area carbons) as well as binder materialsfor enhancing mechanical integrity of the layer.

In various embodiments fully solid-state battery cell 1600C is composedof positive and negative electrodes that are each composite powdercompacts or tape cast layers, separated by a solid electrolyte sheet ofthe present disclosure (e.g., a vitreous sheet of a Li ion conductingsulfide based glass).

In another aspect, the solid electrolyte sheet of the present disclosuremay be used as an interlayer in a protective membrane architecture as aLi ion conducting layer disposed between a substantially imperviouslithium ion conducting membrane and a Li metal anode layer. Theincorporation of a vitreous sulfide based solid electrolyte sheet inaccordance with various embodiments of the present disclosure as aninterlayer provides improved performance as the vitreous solidelectrolyte sheet is devoid of pathways for through penetration oflithium metal dendrites. Protective membrane architectures and protectedlithium electrode architectures are fully described in Applicant'sco-pending patent applications and issued patents, including U.S. Pat.Nos. 7,282,296; 7,390,591; 7,282,295; 8,129,052; 7,824,806; and U.S.Pat. Pub. No.: 20140170465, all of which hereby incorporated byreference.

With reference to FIG. 16D there is illustrated a process for making alithium metal battery cell 1600D that, in its as-fabricated state, isdevoid or substantially devoid of lithium metal. The cell is composed ofcell laminate 1601D comprising: i) electrode subassembly 1100B havingcurrent collecting layer 1101 b and optional tie layer 1101 a, asdescribed above with reference to FIG. 11B; and ii) positive electrode1660 comprising electroactive layer 1662 and current collecting layer1664. In some embodiments cell 1600D has a hybrid cell construction,with a liquid electrolyte impregnated as described with reference toFIG. 16B. In other embodiments cell 1600D may be a solid-state batterycell, and therefore absent liquid electrolyte and its associatedseparator layer 1670. Continuing with reference to FIG. 16D,electroactive layer 1662 is a fully lithiated lithium intercalationmaterial layer, and is the sole source of Li capacity in theas-fabricated cell. Lithium metal 1662 is formed as a result of theinitial cell charge, as Li from layer 1662 is plated onto electrodesubassembly 1100B, thereby producing lithium metal component layer 1620.In another embodiment laminate 1100B may be provided by lithium metalelectrode assembly 1300 having a scant amount of lithium metal (e.g., <1μm thick), which as described above with reference to FIG. 13B is usedtherein as a bonding layer, and herein also provides a seed layer, forenhancing uniform plating onto the current collector layer.

With reference to FIG. 16E there is illustrated a lithium metal batterycell in accordance with the present disclosure; the cell is composed ofpositive electrode assembly 1500 (shown in detail in FIG. 15 ) andlithium metal layer 1310-1 and 1310-2 disposed in direct contact withfirst surface 101A of respective solid electrolyte sheets 100-1 and100-2.

In various embodiments the solid electrolyte sheet of the presentdisclosure and components thereof are inspected for quality control, andin particular spectrophotometry methods are used to characterize thesurfaces and interfaces.

In various embodiments light attenuation is used to characterize astandalone vitreous sheet of the instant disclosure. Measurements aremade based on comparison of incident light and transmitted lightintensities at various wavelengths (see the schematic in FIG. 17 ).Light attenuation is determined by light absorption in the vitreoussheet, which is not affected by the presence of glass flaws, and lightscattering due to presence of flaws in the bulk of the vitreous sheetand on its surfaces. Certain types of flaws can lead to lightscattering, including: glass inter-particle boundaries (i.e., particleto particle boundaries), inclusions of crystalline phase due to partialcrystallization, bubbles, cracks, digs, surface scratches. The overallconcentration of scattering centers is approximated from the spectraldependence of light attenuation using Mie theory of independent lightscattering on spherical particles. Since light-scattering flawsgenerally have a more complex shape, accurate quantitative determinationof scattering center concentration is quite difficult. However,approximation based on spherical particles can be used forsemi-quantitative characterization of light-scattering flaws in glasslayers. In the quality control method contemplated herein, incidentlight intensity is kept constant and transmitted light intensities forglass layers of the same thickness are compared with a reference sampleof acceptable quality, as determined from electrochemical cycling data(improved protection of Li metal or Li alloy electrode that manifestsitself as an increase in lithium cycling efficiency and number ofcharge/discharge cycles).

In various embodiments the light reflection from a metal surface incontact with the vitreous sheet is used for characterization of such asubstrate laminate such as for an electrode subassembly or electrodeassembly of the instant disclosure. If vitreous sheet is coated with ametal film (in particular with vacuum deposition), light reflection fromthe metal film interface with the vitreous layer (internal interface) isused to evaluate concentrations of scattering centers in the bulk of thevitreous sheet and on the vitreous sheet-metal interface (see theschematic in FIG. 18 ). In this case, we compare the reflected lightintensities with a reference sample consisting of a completelytransparent silicate glass slide coated with the same metal film. Themeasured reflected light intensity is reduced because both incident andreflected light intensities are attenuated by the scattering flaws inthe bulk of the sheet. For this purpose, metals with reflectioncoefficients close to 100% (Al, Ag) are used.

In one important embodiment, the metals in contact with the vitreoussheet are Li alloy-forming metals, such as Ag, Sn, Al, In, that form areactive bond between Li metal and the sheet (see the schematic in FIGS.19A-B). After Li reacts with the alloy-forming metal, the reflectioncoefficient of the solid electrolyte sheet-metal interface dropssignificantly (by 20%, 30%, 40%, 50% or greater), since instead of beingreflected from a metal with close to 100% reflection coefficient (suchas Ag), the light is now reflected from a Li-alloy surface. Underconditions when there is an excess of lithium metal compared to an alloyforming metal, the alloy forming metal will be lithiated and convertedinto a Li-Metal intermetallic or alloy compound with the highestpossible lithium content. The reflection from the Li-Metal intermetalliccompound can be diffuse rather than mirror-like, and the reflected lightintensity is measured using a spectrophotometer equipped with integratedspheres that are coated with highly reflective materials, such as MgO orBaSO₄. This method allows for visualization of surface flaws at thevitreous sheet-Li alloy interface. In particular, if Li foil or layer ispartially delaminated from the vitreous sheet surface or has areas withlower reactivity, for example due to inclusions of Li nitride or surfacefilms that are thicker than in other areas of contact, the formation ofLi intermetallic compound in these areas will be delayed or, in somecases, will not occur at all. In one embodiment, changes in reflectivityof the interface are monitored, in particular recorded on video, inorder to identify areas of low Li reactivity.

FIG. 20 illustrates changes in reflection coefficient measured over timein the structure from FIG. 19 . Region A corresponds to reflection frommetal surface (before Li alloy is formed on reflective surface). RegionB illustrates a gradual drop in reflection coefficient value during thetransition period. The intermediate values of reflection coefficient canbe attributed to either non-uniform conversion of metal surface to Lialloy over the measured surface area or to incomplete conversion ofmetal surface to Li alloy with the highest Li metal content or to thecombination of both processes. Region C corresponds to reflection fromsurface of Li rich intermetallic compound after its formation iscomplete and the system is in a steady state.

In another important embodiment, the metal in contact with the vitreoussheet is Li metal, in particular extruded Li foil or vacuum deposited orelectrodeposited Li film. In this case, the light is reflected from theLi surface bonded to the glass layer. Depending on the Li surfacemorphology, the reflection can be either mirror-like or diffuse.Incomplete Li coating, areas of low Li reactivity or areas lackingintimate contact between Li and the vitreous sheet surface arevisualized as areas with low reflection coefficient. In one embodiment,Li surface condition in a fabricated Li-sheet laminate is characterizedby measurements of reflection coefficient and its changes over time. Inanother embodiment, the reflection coefficient is measured in situ, inan assembled cell equipped with an optical window, allowing forcharacterization of Li surface morphology at various stages ofelectrochemical cycling and during cell storage.

In various embodiments characterization and quality control of theinstant vitreous sheet and the interfaces it makes with Li and Li alloysin lithium electrode assemblies of the instant disclosure are made usingmeasurements of local resistance.

In one embodiment, measurements are performed in a solid-state cell(FIG. 21A-B). Resistance across the instant sheet is measured in variouslocations on the sheet surface. In this case, one electrode with a smalltip, or a “probe”, moves along the sheet surface. The probe diameter isin the range of 10 um-1 mm. In order to minimize the “current linespread” that decreases the accuracy of local resistance measurements,the sheet thickness is chosen from the range of 5 um-100 um. The second(counter) electrode with a significantly larger surface area (up to thefull area of the glass layer) is located on the opposite side of thesheet (i.e., second principal side) and is stationary. The probe is madeof a soft inert metal (not Li), such as Au, In, Ga, etc., that does notscratch or in any other way damage the sheet surface while maintainingreliable contact with the sheet. In this embodiment, the secondelectrode is not Li and could be the same metal as in the probe. Localresistance of the sheet is determined from AC impedance spectra. Forquality control of sheet uniformity, a maximum acceptable deviationvalue of local resistance is set (e.g., 1%, 2%, 5%, 10% of average localresistance).

In one embodiment, the second electrode with a large area is a Li alloyforming metal, such as Ag, Sn, Al, In. In this case, after the solidelectrolyte sheet is characterized by its local resistance, it can beused for fabrication of a Li alloy-solid electrolyte sheet laminate,since the quality control method is non-destructive. In anotherembodiment, measurements of local resistance along the sheet surface areperformed with a larger probe to obtain a large scale map of surfaceflaws, and then the resistance is measured with a smaller probe toobtain a more detailed distribution of local surface flaws.

In one embodiment, impedance measurements are performed in a cellsimilar to the one described above, but having a liquid non-aqueouselectrolyte located between the vitreous sheet and the counter electrode(FIG. 22 A-B). The liquid non-aqueous electrolyte can be containedwithin the pores of a Celgard-type separator. The nonaqueous electrolytecontains a Li salt (LiTFSI, LiFSI, LiPF₆) and an aprotic solvent orsolvent mixtures, in particular such solvents as ethers (DME, dioxolane)or organic carbonates (DMC, EEC, PC, EC). The advantage of this methodis that once the resistance measurements are performed on one side ofthe sheet (e.g., first principal side), the test cell can bedisassembled, the non-aqueous electrolyte can be rinsed off with anonaqueous solvent, and the resistance measurements can be repeated onthe second principal side, since the method is non-destructive.

CONCLUSION

Although this disclosure provides some detail for purposes of clarity ofunderstanding, it will be apparent that certain changes andmodifications may be practiced within the scope of this disclosure. Itshould be noted that there are many alternative ways of implementingboth the process and compositions of this disclosure. Accordingly, thepresent embodiments are to be considered as illustrative and notrestrictive, and this disclosure is not to be limited to the detailsgiven herein. For instance, the intrinsically Li ion conductive glassesdescribed above are embodied by sulfide glasses, however it is to beappreciated that the description in many aspects is broadly applicableto other, as yet undiscovered, highly conductive inorganic glasses suchas Li ion conducting oxides, phosphates, oxynitrides, and silicateglasses, which may be devoid of sulfur. Moreover, while the solidelectrolyte wall structures (e.g., vitreous sheets) of this disclosureare generally intended for use in an electrochemical device such as abattery cell, they are, nonetheless, standalone material components thatare fabricated apart from the device or electrode assembly into whichthey are ultimately incorporated, and may also be stored and/ortransported independently as discrete battery cell components. Theutility of the Li ion conducting solid electrolyte wall structures andsheets disclosed herein are therefore more generally applicable to avariety of electrochemical devices that require Li ion conduction.

The invention claimed is:
 1. A method for making a standalone Li ionconductive solid electrolyte separator, the method comprising making avitreous solid sheet of Li ion conducting sulfur-based glass; whereinthe method for making the vitreous sheet comprises the steps of: a.forming a continuous fluid sheet of an inorganic sulfur-based glass at atemperature above T_(g) of the glass, the fluid sheet havingsubstantially parallel lengthwise edges and a center portion havingfirst and second opposing principal side surfaces; b. causing thecontinuous fluid sheet to flow with unbroken continuity; c. solidifyingthe continuous fluid sheet by cooling it to a temperature below T_(g);wherein the solidified fluid sheet of sulfur-based glass is vitreous,substantially amorphous, conductive of Li ions, and of unbrokencontinuity; and wherein just prior to reaching a temperature at or belowT_(g), the first and second principal side surfaces are untouched by aforeign solid surface; and further comprising the step of removingperipheral lengthwise edge portions of the sheet by laser cutting. 2.The method of claim 1, wherein the center portion of the fluid sheet hasuniform thickness (t) selected from the group consisting of 250 mm<t≤500mm (±10%); 100 mm<t≤250 mm (±20%); 50 mm<t≤100 mm (±20%); 30 mm<t≤50 mm(±20%); and 10 mm<t≤30 mm (±20%).
 3. The method of claim 1, wherein thesolidified fluid sheet is at least 10 cm long.
 4. The method of claim 1,wherein the fluid sheet of sulfur-based glass is a fluid stream ofunbroken continuity that is derived directly from a liquid melt andcaused to flow along its lengthwise dimension.
 5. The method of claim 1,wherein the mole % of Li in the sulfur-based glass is >10%.
 6. Themethod of claim 1, wherein the fluid sheet is a fluid stream of unbrokencontinuity that is not derived directly from a liquid melt.
 7. Themethod of claim 1, wherein the forming step comprises: i) providing asolid vitreous preform of the sulfur-based glass; ii) heating a sectionof the preform to a temperature above T_(g) but below T_(liq); iii) andcausing the heated section of the preform to flow.
 8. The method ofclaim 7, wherein the fluid sheet is caused to flow by a pulling forceapplied to the heated section of the preform.
 9. The method of claim 1,wherein the sulfur-based glass has glass stability factor less than 50°C.
 10. The method of claim 1, wherein the sulfur-based glass has glassstability factor less than 30° C.
 11. The method of claim 1, wherein thevitreous solid sheet of Li ion conducting sulfur-based glass isessentially free of crystalline phases.
 12. The method of claim 1,further comprising the steps of: i) selecting constituent elements ofthe sulfur-based glass, the constituent elements comprising S (sulfur),Li (lithium), and one or more of P (phosphorous), B (boron), Si(silicon), and O (oxygen); and ii) adjusting the mole ratio of theconstituent elements to increase the liquidus viscosity, withoutdecreasing the room temperature Li ion conductivity of the sheet below10⁻⁵S/cm.
 13. The method of claim 12, wherein the adjusting stepcomprises not decreasing the room temperature Li ion conductivity below10⁻⁴S/cm.
 14. The method of claim 12, wherein the liquidus viscosity isgreater than 200 poise.
 15. The method of claim 12, wherein the liquidusviscosity is greater than 1,000 poise.
 16. The method of claim 12,wherein the adjusting step does not increase the ASR to a value greaterthan 200 W-cm², as measured between opposing principal side surfacesusing non-blocking lithium metal electrodes.
 17. The method of claim 1,further comprising the steps of: i) selecting constituent elements ofthe inorganic sulfur-based Li ion conducting glass, the constituentelements comprising S (sulfur), Li (lithium), and one or more of P(phosphorous), B (boron), Si (silicon), and O (oxygen); and ii)adjusting the mole ratio of the constituent elements to increase theglass stability factor {T_(g)−T_(g)} of the sulfur-based glass, withoutdecreasing the room temperature Li ion conductivity of the sheet below10⁻⁵S/cm.
 18. The method of claim 17, wherein the room temperature Liion conductivity does not decrease below 10⁻⁴ S/cm.